ROMs are copyrighted content and as such are not included with Retro Pie.
A BIOS is a small piece of software that tells hardware how to work.
BIOSs are also copyrighted and are therefore not included with Retro Pie.
With the md5 file you can verify all downloaded parts with an external program (example https:// that they are complete.The Retro Pie SD image comes pre-installed with many different emulators.Additional emulators may be installed from within Retro Pie. Loading up a ROM in an emulator is the equivalent of putting a cartridge in a game console.Im not using Romcenter, but it does reports incomplete sets.There should be an option to displays it or to safe those information .....