Only download ROMs for games you physically own on the original media (e.g., a phone with the game pre-loaded or an arcade board). However, because phone-based games were rarely sold on cartridges, the community generally tolerates preservation of "endangered" ROMs—those no longer sold or supported anywhere.
In the past, retro gaming required installing individual emulators for every single console. Modern emulation has shifted toward unified frontends and software suites. mobasuite roms