Billi Rosen was born in 1942 in Greece, where she spent the first years of her childhood. She was educated in Sweden and then moved to the United Kingdom in her late teens. She subsequently traveled extensively in Europe, living in Italy, Switzerland and on the Greek island of Corfu. Today, she divides her time between Portsmouth (United Kingdom) and Corfu.

She has three children.

Rosen is a multi-talented woman, and in addition to her career as a notable author of children's and young adult books, she has worked in education, in television, and also as a freelance photographer and journalist.

Rosen's first book for children, Andi's War, won the Faber/Guardian/Jackanory Children's Competition for unpublished authors for children in 1987 as well as the Prix Enfance du Monde Natha Caputo (UNICEF) in 1993. Furthermore, Andi's War was serialized for the BBC television program Jackanory. Since...