Maybe this sounds like a very stupid question to most of you but I always wondered about it.
Where do the ROMs come from in the first place? Who turns the game data into executable files? Of course everyone heard of fan made groups like Emulator Designers (SNES9X, ZSNES) and dubbers (DEJAP), but I’ve never heard of any group that actually makes the ROMs. Also, they seem to come out almost at the same time as the actual games do.
Have you ever tried decompiling a rom? I’ve tried an emu, some are really straight forward, like Dgen but, snes9x is totally hardcore, like forever in notepad.
For older games there is a “rom dumper” or something that you put the cartridge in and it takes the information. Zophar has links to where you can buy these sorts of things.