Right now the temporary runtime config files created and loaded by NETCoreCheck never have any value specified for the roll forward policy, which limits it's usefulness for determining whether or not a particular .NET app will be able to run. We should add a third parameter to NETCoreCheck for the roll forward policy. For example, running:

NETCoreCheck.exe Microsoft.WindowsDesktop.App 3.1.0 LatestMajor

Should internally create a runtime config file that looks like this:

"runtimeOptions": {
  **"rollForward": "LatestMajor",**
  "framework": {
    "name": "Microsoft.WindowsDesktop.App",
    "version": "3.1.0"
  }
}

An example difference is that if this were run on a machine with just the 5.0.x Windows Desktop runtime the check would now pass.

For more information on roll forward policies see dotnet/docs#12237