It's an N64 game. N64 games can (normally) only run on an N64. The N64 emulator is software that lets the PC 'pretend' to be an N64 so it can run N64 games, but the N64 emulator isn't perfect. ROMs are N64 games turned into PC files. The emulator reads them the same way the N64 reads a cartridge.
The reason someone made a ROM of the game even though N64 emulators can't read it is so that people who improve N64 emulators can use it as a test, and maybe play it one day, but not now.
So unfortunately, the answer is that you just can't play it. We're not keeping anything from you.