Taken to the circle quite young (~5 years old), Rosamund really doesn't remember much of her life or her family before then.
She DOES remember her mother (or a woman she assumes to be her mother - her face is blurry in Rosamund's memory) screaming in the street and being restrained as Rosamund was taken away by the Templars. The woman begged her to obey the Templars, to follow their rules and stay safe until she came to fetch her, so that's what Rosamund did - even after she had given up hope that her family was coming for her.
Because she's well-behaved and eager to learn, Rosamund excels in the Circle, although she doesn't have much in common with the other children. By the time peers her age start to arrive, she's already been at the Circle for years and is therefore a bit of a know-it-all when it comes to the all-important rules and learning how to control one's powers. She also has little desire to get out, and whereas children who came to the Circle recently and still remember their families are understandably homesick, Rosamund has already accepted her situation.
herbalism, healing, potion making... Rosamund is a very proficient student and powerful mage and excels at AoE attacks and (although she didn't really hone this until after leaving the Circle, as this was hard to practice indoors) lightning magic.
Reluctant class project partners with a trauma bond (... to lovers): Alistair
Cool cousin who begrudgingly really enjoys her company: Morrigan
Wise bisexuals watching over this poor nerd like an angel and devil on her shoulders: Leliana & Zevran
Older female role model (I hesitate to say "mother figure") clearly processing some trauma externally: Wynne
Rosamund's mother: the only one of her family Rosamund can remember, and even then, her mother is just a wailing figure with dark hair in her memory
First Enchanter Irving: officially the one charged with Rosamund's care at the Circle, although several other adult mages "shared custody"
Wynne: one of Rosamund's unoffical guardians; they're quite fond of one another as their talents for healing overlap and Rosamund learned quite a bit from Wynne
Jowan: a few years older than Rosamund, but her first friend at the Circle. She enjoys bossing him around and he enjoys following her (usually) capable instructions
Cullen: these two little goody-two-shoes(es?) have a tooth-rottingly-sweet mutual crush that neither of them know what to do about