The core generates a .cfg file in the root RetroArch directory.
You will find many lines that have to do with various rom paths. I have 4 roms:
I’m just posting my paths as an example. Make sure your paths are correct in the cfg file. You can see the folder structure and names as well. You probably don’t need all these roms (the 5200.rom is the one you really need) but i’m not sure. I just happen to have those.