diff --git a/eng/Subsets.props b/eng/Subsets.props
index f2480616431b5..ce90e8748f887 100644
--- a/eng/Subsets.props
+++ b/eng/Subsets.props
@@ -336,7 +336,8 @@
                              $(CoreClrProjectRoot)tools\r2rdump\R2RDump.csproj;
                              $(CoreClrProjectRoot)tools\dotnet-pgo\dotnet-pgo.csproj;
                              $(CoreClrProjectRoot)tools\aot\ILCompiler\repro\repro.csproj;
-                             $(CoreClrProjectRoot)tools\r2rtest\R2RTest.csproj" Category="clr" Condition="'$(DotNetBuildFromSource)' != 'true'"/>
+                             $(CoreClrProjectRoot)tools\r2rtest\R2RTest.csproj;
+                             $(CoreClrProjectRoot)tools\AssemblyChecker\AssemblyChecker.csproj" Category="clr" Condition="'$(DotNetBuildFromSource)' != 'true'"/>
     <ProjectToBuild Include="$(CoreClrProjectRoot)tools\aot\crossgen2\crossgen2.csproj" Category="clr" />
     <ProjectToBuild Include="$(CoreClrProjectRoot)tools\aot\ILCompiler.Build.Tasks\ILCompiler.Build.Tasks.csproj" Category="clr" Condition="'$(NativeAotSupported)' == 'true'" />
     <ProjectToBuild Include="$(CoreClrProjectRoot)tools\aot\ILCompiler\ILCompiler.csproj" Category="clr" Condition="'$(NativeAotSupported)' == 'true'" />
diff --git a/src/coreclr/tools/AssemblyChecker/AssemblyChecker.csproj b/src/coreclr/tools/AssemblyChecker/AssemblyChecker.csproj
new file mode 100644
index 0000000000000..821c47c95403c
--- /dev/null
+++ b/src/coreclr/tools/AssemblyChecker/AssemblyChecker.csproj
@@ -0,0 +1,16 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <AssemblyName>AssemblyChecker</AssemblyName>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>$(NetCoreAppToolCurrent)</TargetFramework>
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+    <AppendTargetFrameworkToOutputPath Condition="'$(BuildingInsideVisualStudio)' == 'true'">true</AppendTargetFrameworkToOutputPath>
+    <GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
+    <EnableDefaultEmbeddedResourceItems>false</EnableDefaultEmbeddedResourceItems>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <OutputPath>$(RuntimeBinDir)\AssemblyChecker</OutputPath>
+    <RunAnalyzers>false</RunAnalyzers>
+  </PropertyGroup>
+</Project>
diff --git a/src/coreclr/tools/AssemblyChecker/Program.cs b/src/coreclr/tools/AssemblyChecker/Program.cs
new file mode 100644
index 0000000000000..69f86e050beb2
--- /dev/null
+++ b/src/coreclr/tools/AssemblyChecker/Program.cs
@@ -0,0 +1,117 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Text;
+using System.Diagnostics;
+using System.Reflection;
+using System.Reflection.Metadata;
+using System.Reflection.PortableExecutable;
+
+namespace AssemblyChecker
+{
+    /// <summary>
+    /// This is a simple console application that is designed to answer True or False
+    /// questions about whether a given file is a managed assembly or not.
+    /// You can also ask whether or not the assembly is debuggable.
+    /// Return code of 0 indicates the file is a managed assembly.
+    /// Return code of 1 indicates the file is not a managed assembly. No errors will be printed for this one.
+    /// </summary>
+    public class Program
+    {
+        private const string HelpText = @"
+Usage:
+    <filePath>: Check if the file-path is a managed assembly.
+    --is-debug <filePath>: Check if the file-path is a managed assembly that is built with debuggability.
+    --is-exe <filePath>: Check if the file-path is a managed assembly that is an executable.
+";
+
+        static bool IsAssembly(string path)
+        {
+            using var fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
+
+            // Try to read CLI metadata from the PE file.
+            using var peReader = new PEReader(fs);
+
+            if (!peReader.HasMetadata)
+            {
+                return false; // File does not have CLI metadata.
+            }
+
+            // Check that file has an assembly manifest.
+            MetadataReader reader = peReader.GetMetadataReader();
+            return reader.IsAssembly;
+        }
+
+        static bool IsDebug(string path)
+        {
+            return
+                Assembly.LoadFrom(path)
+                .GetCustomAttributes(typeof(DebuggableAttribute), false)
+                .OfType<DebuggableAttribute>().Any(x => x.IsJITOptimizerDisabled);
+        }
+
+        static bool IsExe(string path)
+        {
+            using var fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
+
+            // Try to read CLI metadata from the PE file.
+            using var peReader = new PEReader(fs);
+
+            if (!peReader.HasMetadata)
+            {
+                return false; // File does not have CLI metadata.
+            }
+
+            return peReader.PEHeaders.IsExe;
+        }
+
+        static int Main(string[] args)
+        {
+            if (args.Length == 0)
+            {
+                Console.WriteLine(HelpText);
+                Console.Error.WriteLine("\nExpected assembly file-path.");
+                return 2;
+            }
+
+            // Help
+            if (args.Contains("-h"))
+            {
+                Console.WriteLine(HelpText);
+                return 0;
+            }
+
+            if (args.Length == 1)
+            {
+                return IsAssembly(args[0]) ? 0 : 1;
+            }
+
+            if (args.Length == 2)
+            {
+                switch (args[0])
+                {
+                    case "--is-debug":
+                        {
+                            return IsDebug(args[1]) ? 0 : 1;
+                        }
+
+                    case "--is-exe":
+                        {
+                            return IsExe(args[1]) ? 0 : 1;
+                        }
+
+                    default:
+                        {
+                            Console.WriteLine(HelpText);
+                            Console.Error.WriteLine("\nInvalid option.");
+                            return 2;
+                        }
+                }
+            }
+
+            Console.WriteLine(HelpText);
+            Console.Error.WriteLine("\nToo many arguments.");
+            return 2;
+        }
+    }
+}
diff --git a/src/tests/Common/CLRTest.Execute.Bash.targets b/src/tests/Common/CLRTest.Execute.Bash.targets
index ea33ed79bad9b..81a50db81cacc 100644
--- a/src/tests/Common/CLRTest.Execute.Bash.targets
+++ b/src/tests/Common/CLRTest.Execute.Bash.targets
@@ -381,8 +381,6 @@ else
     LAUNCHER="$_DebuggerFullPath $_DebuggerArgsSeparator $(CLRTestRunFile)"
 fi
 
-$(BashIlrtTestLaunchCmds)
-
 if [ ! -z ${RunCrossGen2+x} ]%3B then
   TakeLock
 fi
@@ -412,8 +410,6 @@ else
     LAUNCHER="$_DebuggerFullPath $_DebuggerArgsSeparator $(CLRTestRunFile)"
 fi
 
-$(BashIlrtTestLaunchCmds)
-
 if [ ! -z ${RunCrossGen2+x} ]%3B then
   TakeLock
 fi
diff --git a/src/tests/Common/CLRTest.Execute.Batch.targets b/src/tests/Common/CLRTest.Execute.Batch.targets
index 90ba71856b72e..f19c8987bbc6f 100644
--- a/src/tests/Common/CLRTest.Execute.Batch.targets
+++ b/src/tests/Common/CLRTest.Execute.Batch.targets
@@ -318,8 +318,6 @@ IF NOT "%CLRCustomTestLauncher%"=="" (
   set LAUNCHER=%_DebuggerFullPath% $(CLRTestRunFile)
 )
 
-$(BatchIlrtTestLaunchCmds)
-
 if defined RunCrossGen2 (
   call :TakeLock
 )
diff --git a/src/tests/Common/CLRTest.Jit.targets b/src/tests/Common/CLRTest.Jit.targets
index 9748b6424f737..476595df0c8be 100644
--- a/src/tests/Common/CLRTest.Jit.targets
+++ b/src/tests/Common/CLRTest.Jit.targets
@@ -62,66 +62,16 @@ export RunningIlasmRoundTrip=
 
 if [ -z "$DoLink" -a ! -z "$RunningIlasmRoundTrip" ];
 then
-  mkdir IL-RT
-  cp $(InputAssemblyName) $(TargetAssemblyName)
-  echo "$CORE_ROOT/ildasm" -raweh -unicode -out=$(DisassemblyName) $(TargetAssemblyName)
-  "$CORE_ROOT/ildasm" -raweh -unicode -out=$(DisassemblyName) $(TargetAssemblyName)
+  python3 $(AssemblyName)_ilasmroundtrip.py
   ERRORLEVEL=$?
   if [ $ERRORLEVEL -ne 0 ]
   then
-    echo EXECUTION OF ILDASM - FAILED $ERRORLEVEL
-    exit 1
-  fi
-  if [ ! -f "$(DisassemblyName)" ]
-  then
-    echo "EXECUTION OF ILDASM - FAILED $(DisassemblyName) is missing"
-    exit 1
-  fi
-
-  ilasm_count=1
-  while true
-  do
-    echo "$CORE_ROOT/ilasm" -output=$(InputAssemblyName) $(_IlasmSwitches) $(DisassemblyName)
-    "$CORE_ROOT/ilasm" -output=$(InputAssemblyName) $(_IlasmSwitches) $(DisassemblyName)
-    ERRORLEVEL=$?
-    if [ $ERRORLEVEL -eq 0 ]
-    then
-      break
-    fi
-
-    echo EXECUTION $ilasm_count OF ILASM - FAILED with $ERRORLEVEL
-
-    if [ $ilasm_count -eq 3 ]
-    then
-      break
-    fi
-
-    ((ilasm_count++))
-    echo Trying again
-    sleep 10
-  done
-
-  if [ $ERRORLEVEL -ne 0 ]
-  then
+    echo ILASM ROUND-TRIP - FAILED $ERRORLEVEL
     exit 1
   fi
 fi
 ]]>
       </IlasmRoundTripBashScript>
-      <BashIlrtTestLaunchCmds Condition="'$(CLRTestKind)' == 'BuildAndRun'"><![CDATA[
-if [ -z "$DoLink" -a ! -z "$RunningIlasmRoundTrip" ];
-then
-  echo $LAUNCHER $(InputAssemblyName) %24(printf "'%s' " "${CLRTestExecutionArguments[@]}")
-  $LAUNCHER $(InputAssemblyName) "${CLRTestExecutionArguments[@]}"
-  ERRORLEVEL=$?
-  if [ $ERRORLEVEL -ne $CLRTestExpectedExitCode ]
-  then
-    echo END EXECUTION OF IL{D}ASM BINARY - FAILED $ERRORLEVEL vs $CLRTestExpectedExitCode
-    exit 1
-  fi
-fi
-]]>
-      </BashIlrtTestLaunchCmds>
     </PropertyGroup>
   </Target>
 
@@ -144,54 +94,18 @@ set RunningIlasmRoundTrip=
 REM IlasmRoundTrip Script
 REM Disable Ilasm round-tripping for Linker tests.
 REM Todo: Ilasm round-trip on linked binaries.
+
 IF NOT DEFINED DoLink (
   IF DEFINED RunningIlasmRoundTrip (
-    mkdir IL-RT
-    copy $(InputAssemblyName) $(TargetAssemblyName)
-    ECHO %CORE_ROOT%\ildasm.exe /raweh /unicode /out=$(DisassemblyName) $(TargetAssemblyName)
-    %CORE_ROOT%\ildasm.exe /raweh /unicode /out=$(DisassemblyName) $(TargetAssemblyName)
-
+    python $(AssemblyName)_ilasmroundtrip.py
     IF NOT "!ERRORLEVEL!"=="0" (
-      ECHO EXECUTION OF ILDASM - FAILED !ERRORLEVEL!
-      Exit /b 1
-    )
-    IF NOT EXIST $(DisassemblyName) (
-      ECHO EXECUTION OF ILDASM - FAILED $(DisassemblyName) is missing
-      Exit /b 1
-    )
-
-   set ilasm_count=1
-:Try_ilasm
-    ECHO %CORE_ROOT%\ilasm.exe /output=$(InputAssemblyName) $(_IlasmSwitches) $(DisassemblyName)
-    %CORE_ROOT%\ilasm.exe /output=$(InputAssemblyName) $(_IlasmSwitches) $(DisassemblyName)
-    IF NOT "!ERRORLEVEL!"=="0" (
-      ECHO EXECUTION OF ILASM - Try !ilasm_count! FAILED with status !ERRORLEVEL! 
-      IF !ilasm_count! LEQ 3 (
-        ECHO Trying again
-        set /A ilasm_count=ilasm_count+1
-        timeout /t 10 /nobreak
-        goto :Try_ilasm
-      )
-      ECHO EXECUTION OF ILASM - FAILED
+      ECHO ILASM ROUND-TRIP - FAILED !ERRORLEVEL!
       Exit /b 1
     )
   )
 )
 ]]>
       </IlasmRoundTripBatchScript>
-      <BatchIlrtTestLaunchCmds Condition="'$(CLRTestKind)' == 'BuildAndRun'"><![CDATA[
-IF NOT DEFINED DoLink (
-  if defined RunningIlasmRoundTrip (
-    ECHO %LAUNCHER% $(InputAssemblyName) %CLRTestExecutionArguments%
-    %LAUNCHER% $(InputAssemblyName) %CLRTestExecutionArguments%
-    IF NOT "!ERRORLEVEL!"=="%CLRTestExpectedExitCode%" (
-      ECHO END EXECUTION OF IL{D}ASM BINARY - FAILED !ERRORLEVEL! vs %CLRTestExpectedExitCode%
-      Exit /b 1
-    )
-  )
-)
-]]>
-      </BatchIlrtTestLaunchCmds>
     </PropertyGroup>
   </Target>
 
@@ -365,6 +279,109 @@ set DOTNET_JitPath=%CORE_ROOT%\superpmi-shim-collector.dll
     </PropertyGroup>
   </Target>
 
+  <!--
+  ***********************************************************************************************
+  IlasmRoundTrip for merged tests
+  ***********************************************************************************************
+  -->
+
+  <Target Name="IlasmRoundTripCommand" AfterTargets="AfterBuild" Condition="'$(IlasmRoundTripIncompatible)' != 'true'">
+    <PropertyGroup>
+      <InputAssemblyName>$(AssemblyName).dll</InputAssemblyName>
+      <DisassemblyName>IL-RT/$(AssemblyName).il</DisassemblyName>
+      <TargetAssemblyName>IL-RT/$(AssemblyName).dll</TargetAssemblyName>
+      <_IlasmRoundTripScriptText><![CDATA[
+import os
+import shutil
+import subprocess
+import sys
+import glob
+
+def is_managed_assembly(file):
+    proc = subprocess.Popen([f'{os.environ["CORE_ROOT"]}/corerun', f'{os.environ["CORE_ROOT"]}/AssemblyChecker/AssemblyChecker.dll', file])
+
+    try:
+        proc.communicate()
+        return proc.returncode == 0
+    except:
+        proc.kill()
+        return False
+
+def is_managed_debug_assembly(file):
+    proc = subprocess.Popen([f'{os.environ["CORE_ROOT"]}/corerun', f'{os.environ["CORE_ROOT"]}/AssemblyChecker/AssemblyChecker.dll', "--is-debug", file])
+
+    try:
+        proc.communicate()
+        return proc.returncode == 0
+    except:
+        proc.kill()
+        return False
+
+def is_managed_exe_assembly(file):
+    proc = subprocess.Popen([f'{os.environ["CORE_ROOT"]}/corerun', f'{os.environ["CORE_ROOT"]}/AssemblyChecker/AssemblyChecker.dll', "--is-exe", file])
+
+    try:
+        proc.communicate()
+        return proc.returncode == 0
+    except:
+        proc.kill()
+        return False
+
+print("")
+print("ILASM RoundTrips")
+
+if not os.path.exists("IL-RT"):
+  os.mkdir("IL-RT")
+
+for inputAssemblyName in glob.glob("*.dll"):
+  if is_managed_assembly(inputAssemblyName):
+      print("ILASM RoundTrip for " + inputAssemblyName)
+
+      ilasmSwitches = ""
+
+      if not is_managed_exe_assembly(inputAssemblyName):
+        ilasmSwitches = ilasmSwitches + " -DLL"
+
+      if is_managed_debug_assembly(inputAssemblyName):
+        ilasmSwitches = ilasmSwitches + " -DEBUG"
+
+      disassemblyName = os.path.join("IL-RT", os.path.splitext(os.path.basename(inputAssemblyName))[0] + ".il")
+      targetAssemblyName = os.path.join("IL-RT", os.path.basename(inputAssemblyName))
+
+      shutil.copyfile(inputAssemblyName, targetAssemblyName)
+
+      ildasm_args = f'{os.environ["CORE_ROOT"]}/ildasm -raweh -unicode -out={disassemblyName} {targetAssemblyName}'
+      print(ildasm_args)
+      proc = subprocess.Popen(ildasm_args, shell=True)
+
+      try:
+          proc.communicate()
+      except:
+          proc.kill()
+          sys.exit(1)
+
+      ilasm_args = f'{os.environ["CORE_ROOT"]}/ilasm -output={inputAssemblyName} {ilasmSwitches} {disassemblyName}'
+      print(ilasm_args)
+      proc = subprocess.Popen(ilasm_args, shell=True)
+
+      try:
+          proc.communicate()
+      except:
+          proc.kill()
+          sys.exit(1)
+
+      print("")
+
+print("")
+
+]]></_IlasmRoundTripScriptText>
+    </PropertyGroup>
+    <WriteLinesToFile
+      File="$(OutputPath)$(AssemblyName)_ilasmroundtrip.py"
+      Lines="$(_IlasmRoundTripScriptText)"
+      Overwrite="true" />
+  </Target>
+
   <!--
   ***********************************************************************************************
   GCStress settings
diff --git a/src/tests/Common/Directory.Build.targets b/src/tests/Common/Directory.Build.targets
index 5c2707ed55408..1e8e7f8239981 100644
--- a/src/tests/Common/Directory.Build.targets
+++ b/src/tests/Common/Directory.Build.targets
@@ -113,6 +113,11 @@
         <IncludeSubFolders>True</IncludeSubFolders>
       </RunTimeArtifactsIncludeFolders>
 
+      <!-- Used to determine if a file is a managed assembly or a managed assembly built with DEBUG -->
+      <RunTimeArtifactsIncludeFolders Include="AssemblyChecker/" TargetDir="AssemblyChecker/">
+        <IncludeSubFolders>True</IncludeSubFolders>
+      </RunTimeArtifactsIncludeFolders>
+
       <!-- XUnit runner harness assemblies that we don't want to mix in with the framework in Core_Root -->
       <RunTimeArtifactsIncludeFolders Include="xunit/" TargetDir="xunit/" />
     </ItemGroup>
diff --git a/src/tests/JIT/Methodical/fp/exgen/10w5d_cs_do.csproj b/src/tests/JIT/Methodical/fp/exgen/10w5d_cs_do.csproj
index 9eff379e0d455..d1e37c52b6423 100644
--- a/src/tests/JIT/Methodical/fp/exgen/10w5d_cs_do.csproj
+++ b/src/tests/JIT/Methodical/fp/exgen/10w5d_cs_do.csproj
@@ -3,6 +3,7 @@
     <!-- Needed for JIT/superpmi/superpmicollect.csproj which depends on the
          individual test .cmd file -->
     <RequiresProcessIsolation>true</RequiresProcessIsolation>
+    <IlasmRoundTripIncompatible>true</IlasmRoundTripIncompatible>
   </PropertyGroup>
   <PropertyGroup>
     <DebugType>Full</DebugType>
diff --git a/src/tests/JIT/Performance/CodeQuality/Bytemark/Bytemark.csproj b/src/tests/JIT/Performance/CodeQuality/Bytemark/Bytemark.csproj
index 03274a86e59cc..de85a9ce57835 100644
--- a/src/tests/JIT/Performance/CodeQuality/Bytemark/Bytemark.csproj
+++ b/src/tests/JIT/Performance/CodeQuality/Bytemark/Bytemark.csproj
@@ -3,6 +3,7 @@
     <!-- Needed for GCStressIncompatible, UnloadabilityIncompatible -->
     <RequiresProcessIsolation>true</RequiresProcessIsolation>
     <GCStressIncompatible>true</GCStressIncompatible>
+    <IlasmRoundTripIncompatible>true</IlasmRoundTripIncompatible>
     <NoWarn>$(NoWarn);xUnit1013</NoWarn>
     <!-- This test takes a very long time when run with runincontext -->
     <UnloadabilityIncompatible>true</UnloadabilityIncompatible>
diff --git a/src/tests/JIT/Performance/CodeQuality/Roslyn/CscBench.csproj b/src/tests/JIT/Performance/CodeQuality/Roslyn/CscBench.csproj
index 37d4ba53a4c2b..045dc9053d1af 100644
--- a/src/tests/JIT/Performance/CodeQuality/Roslyn/CscBench.csproj
+++ b/src/tests/JIT/Performance/CodeQuality/Roslyn/CscBench.csproj
@@ -6,6 +6,7 @@
     <NoWarn>$(NoWarn);xUnit1013</NoWarn>
     <MonoAotIncompatible>true</MonoAotIncompatible>
     <NativeAotIncompatible>true</NativeAotIncompatible>
+    <IlasmRoundTripIncompatible>true</IlasmRoundTripIncompatible>
   </PropertyGroup>
   <PropertyGroup>
     <DebugType>pdbonly</DebugType>
diff --git a/src/tests/Loader/binding/tracing/BinderTracingTest.ResolutionFlow.csproj b/src/tests/Loader/binding/tracing/BinderTracingTest.ResolutionFlow.csproj
index 0bb68d9cb843d..07f4907e396c9 100644
--- a/src/tests/Loader/binding/tracing/BinderTracingTest.ResolutionFlow.csproj
+++ b/src/tests/Loader/binding/tracing/BinderTracingTest.ResolutionFlow.csproj
@@ -4,6 +4,8 @@
     <UnloadabilityIncompatible>true</UnloadabilityIncompatible>
     <!-- Dynamic assembly loads -->
     <NativeAotIncompatible>true</NativeAotIncompatible>
+    <RequiresProcessIsolation>true</RequiresProcessIsolation>
+    <IlasmRoundTripIncompatible>true</IlasmRoundTripIncompatible>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="BinderTracingTest.EventHandlers.cs" />
diff --git a/src/tests/ilverify/ILVerificationTests.csproj b/src/tests/ilverify/ILVerificationTests.csproj
index 3144da43d0c20..f9f7e7521ffaf 100644
--- a/src/tests/ilverify/ILVerificationTests.csproj
+++ b/src/tests/ilverify/ILVerificationTests.csproj
@@ -5,6 +5,8 @@
     <!-- The test uses xunit directly and it fails to find the test assembly for some reason -->
     <UnloadabilityIncompatible>true</UnloadabilityIncompatible>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <IlasmRoundTripIncompatible>true</IlasmRoundTripIncompatible>
+    <RequiresProcessIsolation>true</RequiresProcessIsolation>
   </PropertyGroup>
 
   <ItemGroup>