Follow this step-by-step guide to create your own randomized ROM.

When downloading ROMs and randomizers:

Select your preferred settings (e.g., "Change Impossible Evolutions" to get Gengar or Alakazam without trading). Click "Randomize (Save)" to generate a new randomized ROM

your settings! You can randomize wild Pokémon, trainer parties, starter choices, item locations, and move sets.

and apply it to a legally obtained ROM file from your own physical cartridge Essential Tools for Randomizing Heart Gold