Typically when you get the “module not found” error when importing PyRosetta, it has to do with there being multiple Python installations on your machine. You may have successfully installed PyRosetta, but you installed if for one Python, whereas when you’re doing the import, you’re doing it in a different Python.
I’d recommend double checking where you installed PyRosetta to, and check to make sure it’s the same Python that you’re using when you get the import error.