Sorry i made this post in haste without more detail. So basically what happens is when you tap Rohseen, for its 4 mana and try adding it any X spell say a hydra that had X(G)(G) The 4 mana to cast the spell will not be added to that x cost. But if the creature has an X ability like Monstrosity the 4 mana that Rosheen can be used for that ability. Tested this on a gold fish game and Tested in a 1v1 commander game with a friend.