Instructions
Play through the game's story mode, and collect 2,000 gil, as well as a Life Stone, Water Stone and Wind Stone. The three Stones are found as random loot in dungeons. Gil is found in dungeons and given as a reward at the end of missions.
Pause the game and select "Shop." Go to the "Accessories" menu and scroll down to the Rosetta Stone. Select it to purchase it with your gil and three Stones.
Look for treasure chests in every dungeon. Many dungeons contain a Rosetta Stone, although it may be difficult to get to. For instance, you might need to slay a particularly tough enemy to reach it the chest.
Complete a dungeon with at least seven Destiny Points (DP) remaining to receive a Rosetta Stone. You start each dungeon with varying amounts of DP, and one point is subtracted each time you battle or change locations. DP is earned by performing well in battle; for instance, not taking any damage generally rewards you with DP.
Beat the final mission of the game to unlock the Blackjack Course in Duel Colosseum, a special game mode. Go to the main menu and select Duel Colosseum. Enter the Blackjack Course. As you play, you earn points. Trade 30 points at the shop to get a Rosetta Stone.