Blackman, 22 has become Blades boss Danny Wilson's sixth signing this summer, with the arrivals of; Matt Hill (Blackpool), Darryl Westlake (Walsall), Shaun Miller (Crewe Alexandra), Tony McMahon (Middlesbrough) and John Cofie (on loan from Manchester United).
The young striker was signing by Rovers from Macclesfield Town in January 2009, but barely featured as his side fell victim to the Premier League trap door last season. He has spent time away on loan and whilst with Motherwell, in November 2010 netted an hat-trick in a 4-0 win over St Johnstone.
He has put pen to paper on a two year deal with an option of a third and could make his debut at home to Burton Albion tomorrow in the Capital One Cup.
In March 2009 he joined Blackpool on loan, playing and scoring at Bramall Lane in a 2-2 draw - he hopes he adds many more to his Lane tally!