Do you have a link, which emulators the built-in retroplayer supports?
Do I need a separate BIOS for every emulator, which retroplayer supports (like a special BIOS for C64)?
Is there a default location, where retrplayer will search for ROM's / BIOS'es (if I want to copy files from my PC)?
retroplayer supports the libretro cores..C64 needs vice_ and no bios as far as I know..although I don't use c64 so better check.. .other bios's in the usual storage/emulators/bios..
retroplayer doesn't search for roms...you add roms from the games section in th UI...like adding movies or tv shows but no artwork yet..