Rosie is a half-blood, as her mother, Alair, is a muggle, and her father, Steve, is a wizard (also a half-blood). Her sister, Joan, is three years younger than her and has yet to come to Hogwarts. Rosie loves writing poetry, acting, and singing, and would like to be an actress or a healer when she grows up. She is a stubborn child, even at her mere 4 feet 10 inches tall, as well as very bright and kind. Her green eyes are oval-shaped, and she has long brown hair and sandy-colored skin. She is a bit insecure under the bubbly and self-confident visage she puts on in front of others.

Rosie's magic surfaced when she was 7. She was doing the dishes and made one of the dishes clean themselves. Before attending Hogwarts, she learned a few simple spells - how to clean dishes with magic, levitating blocks, and unknotting hair.

Rosie's family is in mixed houses. There are a few Gryffindors, although about half of her family are Hufflepuffs, with a few Ravenclaws mixed in. Alair would most likely be a Hufflepuff, as was Steve, although everyone has always expected Joan to be in Ravenclaw. Before coming to Hogwarts, Rosie always wondered what house she would be in. She felt like she was part of every house, but she had a feeling she would be placed in Slytherin because of her passion for acting and her faith in her dreams. She knew she could very well be a Hufflepuff as well, though, because she is very hard-working and really cares about helping others. She also is a strong candidate for Ravenclaw because she loves learning and such, but she is also not afraid to speak her mind and stick to what she believes, making her a prominent choice for Gryffindor. But her suspicions were confirmed when the Sorting Hat put her in Slytherin.