Dorm head of the Clock Tower, and their most powerful member in OLYMPUS. Said to be the most powerful magus in the OLYMPUS, her power coming close to Sorcery. The oldest Master around, being amongst the first one to arrive in the OLYMPUS, and holds the most Duel-Battle victories under her belt, the amount being 88. Defeats her enemies through pure magecraft, and has no need for conceptual weaponry. To defeat her is a short of miracle, or so it is said.
Specializing in a magecraft that has been, apparently, long forgotten by other families than the McKlenningtons, Roselia is one of the few users of "traditional" magecraft that even users of True Magic like Aozaki Aoko, respect, and who is in speaking terms with individuals like Kishua Zelretch Schweinorg. However, despite her apparent, a lot of the woman herself is shrouded in mystery, and even her abilities, as powerful as they must be, are only spoken in whispers amongst other Lords of the Clock Tower.
She is, apparently, a "Natural Magus" whose body does not perceive magic circuits as a foreign invasive entity, and her circuits are a literal part of her body. In this respect, she could be called the antithesis of Souja Mikado. Roselia climbed to the third position in the Duel Chart, while at the same time supporting the flora and fauna of OLYMPUS by herself.
It is known she has used the whole sky as a magic circuit once, and used a spell that tore the same sky asunder for half an hour.
It is said that, among all the Dorm Heads, Roselia has the best Magecraft.