Arcade ROMs must use strict short-coded names (e.g., sfiii.zip for Street Fighter III ). Renaming these files to make them look "cleaner" in a file explorer will immediately cause the emulator to fail because it can no longer identify the game.
Have you fixed your "romset unknown" error? Which game worked for you first? Let us know in the comments below. If you need specific help finding a non-merged datfile, check the official FBNeo documentation for their latest torrent hashes. romset+is+unknown+fbneo+fixed+free