The least devout among the nuns of the Church of Favonius, Rosaria prefers acting in the shadows rather than participating in the activities of the Church. Somewhat intimidating woman who has a rather unorthodox idea of piety. Kaeya describes her as someone who is "honest with herself". She dislikes topics that bore her and having to work overtime. Proficient in killing. Always wears her coif. Uses a polearm, Cryo Elemental Vision.