Born in Durban, South Africa, Rooney came from a sporting family and moved to Alsager, England, when she was four years old. She first became interested in athletics through gymnastics. Rooney was selected to compete at national and international levels, finishing fourth in the British Championships, but did not feel passionate about the sport and changed to pole vault in 2000. She became the first British junior athlete to jump 4.00 metres, as she finished seventh at the 2002 World Junior Championships in Kingston, Jamaica.