Rosalia Rossellini is CR-S01's adopted sister, Albert Sartre's adopted daughter, and Maria Torres' friend while she was staying in the orphanage. She was saved by Maria Torres during a fire that Maria accidentally started in an orphanage.
Rosalia was the natural host to the Rosalia Virus, and held a cure to it within her blood.
Maria is the only one that could see her spirit as Rosalia tried to warn her by appearing as a spirit and saying the last word she said before she died. At one point, she also warned Maria to run right before the school bus accident at the mall where she, Tomoe Tachibana, Hank Freebird and Gabriel Cunningham were in.
Rosalia stayed with Albert Sartre in Mexico while he searched for a cure within her blood. He started experimenting with the blood of Rosalia which caused him to get infected with the Rosalia Virus. Albert tried desperately and as fast as he can to finish the antiserum, but sadly lost his sanity due to the effects of the Rosalia Virus.
Albert thought that by killing Rosalia, he would prevent the Rosalia Virus from spreading. He attempted to shoot her while he was at his desk, but missed Rosalia and hit the window, shattering the glass. Rosalia, figuring out that Albert was out to kill her, ran outside, stepping on shattered glass. She then tried to flee, but was stopped when Albert fired another shot on her right leg. This caused her to collapse on the ground and allow Albert to catch up. While Albert pointed her gun, Rosalia defensively raised her hand, in an act of defensive instinct, but could not prevent the bullet from passing through her hand and into her heart, killing her. While she laid on the ground dying, her last final word was "Beginning..." signifying the start of the pandemic of the Rosalia Virus.
- Rosalia's name may come from Rosalia Lombardo, an Italian girl born in 1918, famous for her extremely well-preserved corpse.
- Due to Rosalia's complexion (pale, almost white platinum blonde and pink eyes) it can be assumed that she might have been albino.
- Rosalia is featured on the Trauma Team Original Soundtrack (HOSPITAL. 6人の医師（Rokunin no Ishi） Original Soundtrack)
- Even though Maria is the only one who is able to see Rosalia's spirit, Naomi appears to see her during 'Carpet of Blue Death' when the case is coming to a resolution.
- When Rosalia is in her scarier looking ghost form, it shows texture that are like the bruises of Rosalia Virus and big red spots where she was shot at.