From my understanding, if you want scanning to work, you need to use No-Intro Roms. I see roms up to Nintendo 64 in packs.
If I want you play PSP, NDS, and Dreamcast, how do I go about adding them to Retroarch? I found a few roms off a site that are of games sitting on my shelf, but it will not scan any of them. It instantly says finished scanning directory.