Disclaimer: The information below is mostly speculative and uses data from unreleased characters obtained from honeyhunter and other leaks. These are all subject to change when it's released.
Rosaria is a Cryo polearm damage dealer that deals a mix of physical and Cryo. This can mean that she can be a strong physical carry because it's easier to cause "Superconduct" reaction with just 1 Electro teammate, or a strong Cryo burst from her skills by bringing a Pyro teammate. Compared to the other 4 star characters, her damage numbers seems to be about average, but the cooldown on her elemental skill is fairly short, and her elemental burst has potential to deal significant damage. But combined with being able to use both Superconduct and Melt gives her some really good potential.
Fischl: One finds Sister Rosaria to be a most devout believer in the Anemo Archon. Oz: ...""Devout believer,"" mein Fräulein? Fischl: Indeed! One night, I heard her invoking the name of the Archon thus in another's presence: ""May you be struck down in the name of Lord Bartabos!"" One presumed that she was leading a prayer.
Some may see Sister Rosaria as one who complains about how bothersome her work is, but she does her job well. Last time I saw her I told her she could come find me should she ever need help, to which she simply replied that doing so would be even more bothersome. I need to work harder to become of more assistance to the people of Mondstadt.
Ahaha, you want to know about the secrets of Sister Rosaria? That... I cannot tell you. Though my impression is not bad — certainly better than a certain someone whose name I won't bother to mention. She's honest with herself. She casts off that which she has no time for and she doesn't feign motivation for affairs that do not interest her.
Sister Rosaria is hard to get to know, especially given she never joins in on prayers, but... Oh, I'm sure she believes in the Anemo Archon! Although, I still don't really have the courage to try to talk to her...
Rosaria attacks in a wide circle with her polearm, forming an area of Cyro energy that damages all enemies inside it. Ice spears fall from the sky, causing further damage.
Passive Talents
Passive Talent
Effect
Night Walk
At night time, from 18:00 to 06:00, any party with Rosaria will have increased movement speed.
Listen to the Shadow of Confession
Increases critical chance during Confession by 12% for 5 seconds.
Darkness Supported by Secrets
Increases the critical chance of all characters in the party while Sacrament of Life is active.
The 1st and the 2nd passives activation requires ascension. See Talents (Skills) Guide for more details.
Constellations
Level
Constellation
Effect
1
Guidance of Sin
Rosaria’s attack speed is increased by 10% after landing Critical Strikes, and the damage is increased by 10%. Both buffs last for 4 seconds.
2
Blessed Land
Elemental Burst duration is increased by 4 seconds.
3
Confession
Increases the skill level of the Confession by 3.
4
Painful Grace
When Confession causes a critical strike, Rosaria regains 5 Elemental Energy.
5
Dying Prayer
Sacrament of Life is increased by three levels.
6
Acting Referee
Elemental Burst reduces enemy physical resistance by 5% for 5 seconds. This effect stacks up to four times.
A Stella Fortuna is required to unlock each constellation. See Constellations Guide for more details.