Rosemary was a very young maid to Kettricken when she came to Buckkeep as Verity's bride. Rosemary was trained to be a spy for Regal. Her father had died before she was born, and her mother lady Celeffa of Firwood had little more than that title to call her own. If she hadn't been in Regal's favour, she would not have come to Buckkeep with her daughter at all.
Rosemary had a habit of drowsing near Kettricken when she was talking "privately" with Fitz. Apparently she repeated the conversations to Regal and even helped arrange an accident that made Kettricken fall in the stairs, though it is unclear whether she realized what she was doing. Kettricken later suspected that it was framed for her as a prank or game.
When Regal returned to Buckkeep after the Red Ship War, Rosemary was with him. Her mother had died and she was neglected because everyone saw that she was no longer in the Queen's favour. She was only 8 years old at that time and a half-trained assassin. Chade talked about it with Kettricken, who was ashamed that she had let the situation become what it was, and went to talk with the girl. Rosemary was frightened of her, but when given the option of either to be fostered to Lady Patience or to be Kettricken's page again, she chose to stay. She is also Chade's apprentice.