Answer by Miroslav Adamec for Could not find a part of the path ... bin\roslyn\csc.exe

I have webproject without csproj file and solutions mentiond here did not work for me.

Changing target .NET framework, reinstalling packages (Update-Package -reinstall) and then building the project worked for me. You can even change target framework back after this operation(make suere you reinstall nuget packages again after).