If you do use a large pack like Retro Legends, you typically need:
The pain point of emulation is configuration. You download a ROM, but the controls are wrong, the screen is stretched, or the sound lags. The comes with pre-configured .cfg files for RetroArch. It auto-detects controllers, applies bezels (virtual CRT scanlines), and even has cheat databases activated. 6666 in 1 rom pack retrolegends