Duelist of the roses ritual card

They are basically magic cards. They allow you to summon strong monsters, provided that you sacrifice the monsters that are specified on the card first.
You can win them by defeating duelists who use them in the game. Some that use them are Tristan, Weevil, Ishizu, and Richard of York. Overall, I would say that they are more trouble than they are worth.
I hope that helps!