Roy "Ronald" Koopa is the one of the Koopalings, making him one of Bowser's children. He appeared in the series as a supporting antagonist in Luigi's Mansion 3: The Room of DOOM!, which is also his only appearance. He is considered to be the older brother of Rocko H. Koopa. The dynamic duo seem to be into each other because they share the same ideas to stop the Mario Bros. from going on their adventure. He is also the younger brother of Donald Koopa, his twin brother.
Ronald is typically a bully to younger kids or older kids with childlike innocence (e.g. Lemmy). He is very skilled when it comes to coming up with an idea to block the Mario Brothers' path. Each time Bowser tells him to do something, he & Rocko do it right away.