He Laughed / Roger Just Laughed - The real reason why Roger was laughing when he got to Laugh Tale

Roger was in fact so pissed about it that he made sure that everyone else embarked on a journey to find the One Piece thinking it's going to be a mountain of gold when in reality it's probably a guy's family picture or something.

I've liked to imagine that when they finally reached the end of the ocean, what they found was a bunch of dicks drawn on a wall