The Irish striker scored seven goals in 28 appearances for the championship side last term and he arrives at The County Ground to bolster Paolo Di Canio’s attacking options.
Rooney signed for Birmingham from Inverness Caledonian Thistle on a two-year-deal in June 2011. In the 2010/11 season he netted 21 goals in 42 games for the Scottish side in the top flight.
The Irishman starred for Crumlin Town as a youth player before pursuing his career in England with Stoke City, for whom he scored four goals in two starts and 17 substitute appearances. In only his second full game Rooney bagged three times against Brighton & Hove Albion in the final fixture of the 2005/06 season, becoming Stoke's youngest ever hat-trick scorer.
After joining Yeovil Town on loan in 2007, Rooney had temporary stints at both Chesterfield and Bury, but it was on moving north of the border in the summer of 2008 that he really started to flourish. After a pre-season trial spell with Inverness he signed a three-year deal with the club.
The frontman, born in Dublin, was voted the 'Irn Bru Phenomenal' Player of the Year at the end of a 2009/10 campaign that saw him finish top scorer in the Scottish First Division with 24 goals and help his team clinch the title. Rooney scored 44 goals in 103 appearances for Inverness, a prolific chapter in a burgeoning career that saw him notch 66 times in an overall total of 181 games before his move to St. Andrew's.
He arrives at Swindon looking to help fire the Robins to success this term and he is expected to be available for Sunday’s League One trip to Preston North End.
Meanwhile, defender Paul Caddis has joined Birmingham City on a season-long loan.