Rosaria is good in physical damage teams but not as the primary damage dealer. She's extremely good when dealing with off-field damage, funneling energy particles, and applying cryo on the enemies. You can use her with Eula to generate energy particles for her so that she gets her elemental burst back faster and trigger massive damage from it. I played a C1 Eula with her signature weapon, and her burst is no joke. There aren't many characters in the game whose elemental burst can obliterate enemies in the blink of an eye. Rosaria paired with Eula is an awesome team-building choice, and I highly recommend Rosaria where you need her abilities.