You will need three things:
Most ORAS randomizers use tools like the Universal Pokémon Randomizer (for PC, generating a patched ROM) or 3DS-specific forks that handle the unique file structure. For this write-up, we assume a with these settings: pokemon alpha sapphire randomizer rom
An idiots guide to using Citra, and randomising the 3DS games. You will need three things: Most ORAS randomizers