Rosetta: The Lost Language is a co-operative judgement game for two or more players.

In the game, players take on the role of experts who try to understand the written language of the author, a player who represents a lost individual, community, or civilization. The author assigns meaning to an inscription that is written in a fictional script, and the experts must figure out what that meaning is. The experts choose a word as a guess, and the author translates it into the given script, informing their understanding of the writing system. This goes back and forth until the experts give a word that is translated into the original inscription. The number of guesses represents a score, with players seeking the lowest score possible.