I understand why Jane had a cupcake and Jake had a pumpkin, but why did Roxy and Dirk have Cotton candy and soda?

Dirk likes orange Soda, and Roxy’s was foreshadowing she has the hots for Jane.

Seriously though, no idea, Hussie likely went with the Food Items he thought would fit them the best. Hell- Did Hussie design Trickster Roxy? First instance of Trickster Roxy was the art Calliope made for her, which was by Shelby, so it may have been a joint effort, and Shelby’s choice to choose Cotton Candy, maybe.