Many "one-size-fits-all" pre-randomized ROMs found online may have issues. Some users have reported that these ROMs can freeze or crash at the starter selection screen. For this reason, Method 1 (the Universal Randomizer) is generally more reliable and recommended.
Download the Universal Pokemon Randomizer ZX (UPR-ZX). This is a safe, open-source Java application that supports generations 1 through 5. Step 2: Running the Universal Pokémon Randomizer pokemon black 2 randomizer rom
: Swapping existing base stat values within a single Pokémon species. Wild Encounter Tables pokemon black 2 randomizer rom