A ROM is a digital copy of the game cartridge. Pokémon Alpha Sapphire is copyrighted by Nintendo, Game Freak, and The Pokémon Company. Distributing a full, untouched ROM is illegal.
However, searching online for a "pre-randomized free ROM download" is highly risky. Sketchy websites often host pre-packaged files loaded with malware or viruses. using your base game and official open-source modding software. Step 1: Secure the Required Tools pokemon alpha sapphire randomizer rom free