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.
She competed at the 2006 Commonwealth Games and was the top English performer, finishing seventh overall. Rooney completed a degree in psychology at Staffordshire University and turned professional, committing herself full-time to the sport. Following graduation, she moved to be trained by Steven Rippon at the centre of excellence in Loughborough.
Rooney won two outdoor tournaments and five indoor titles in the 2007 athletics season. She competed at her first Olympic Games at Beijing 2008 and was knocked out in seventh place in the second heats but set a new outdoor personal best of 4.40 m. Following this she had surgery on both her Achilles, but this did not affect her form in the next season – she broke the national indoor record, beating Janine Whitlock's seven-year-old record, with a jump of 4.45 m at the 2009 UK Indoor Championships in Sheffield, and bettered that mark by another centimetre at the Birmingham Games a week later.
Rooney is the British record holder in pole vault indoors, and she previously held the outdoor record. She beat Janine Whitlock's 4.47 m outdoor record in June 2009. She broke the British record nine times in 2009. Her own outdoor record of 4.60m was beaten by Holly Bleasdale in June 2011, with a jump of 4.70m.
At the 2010 Commonwealth Games in New Delhi, Rooney won a bronze medal in the women's pole vault.