After falling behind to a goal from Brett Emerton in the first half and struggling for a long period of the match, Javier Hernandez was felled by Paul Robinson in the area and Rooney tucked away the penalty to the delight of the fans.
United weren’t quite as efficient as last week against Chelsea when Chicharito rolled the ball home within 40 seconds, but they started well, with Nani rattling the crossbar in the fourth minute.
It was a signal of intent from the champions elect, who were passing the ball menacingly around the edge of Blackburn’s goal area, with Wayne Rooney in particular looking at his dangerous best early on.
Nani came close again in the ninth minute, as Michel Salgado allowed the winger to cut inside, but his effort dragged wide of the near post.
There was a sharp intake of breath for the travelling fans minutes later as Chris Samba was allowed space to volley over from a corner.
And again in the 17
th minute United fans were left drawing for breath, as stand-in goalkeeper Tomasz Kuszczak almost allowed Jason Roberts to score in bizarre circumstances.
The keeper was having a rough patch and it was to cost United dear as Blackburn opened the scoring. The Pole came dashing out to chase down a shot he saved from Brett Emerton, only to turn back and head for goal as the ball was kept in by Martin Olsson. His cross then found its way back to
Emerton, who was only loosely marked by Jonny Evans and the Australian applied the finish.
The poor decision making only served to highlight Ferguson’s dilemma for next season when his No.1. Edwin van der Sar steps down, with a top class goalkeeper his first requirement in the close season.
By the half-hour mark, all United’s good play from the early stages had disappeared. With Blackburn high on confidence and defending well, United look short on ideas. Chicharito forced a stop from Paul Robinson from the edge of the area, but it didn’t threaten too much.
At the other end, Blackburn were testing Kuszczak at every opportunity. He almost handed Rovers another goal as he inexplicably allowed Junior Hoilett to close down a back pass before being tackled, but the ball rebounded for a goal-kick.
Sir Alex Ferguson was already pacing the touchline before added time in the first half, and as the whistle went it was safe to wonder whether Kuszczak would be appearing after half-time, or indeed ever again in a Manchester United shirt.
United came out for the second half as if fresh from a burst of the infamous hairdryer, though Chicharito looked a little off the pace if anything.
Spot on | Wayne Rooney's second half penalty seals United’s 19th title at Ewood Park
Blackburn were continuing their aerial siege on the United goal, and with a less than solid goalkeeper, the nerves were beginning to show in the usually confident pairing of Ferdinand and Vidic.
The title was still tantalisingly close for United though, as Nani’s shot deflected wide off Samba in the 59
th minute, followed by a fantastic block by Phil Jones from a Ryan Giggs shot. The young centre-back was in imperious form in the opening hour, as his stock continues to rise with talk of a summer move to one of England’s top clubs.
In the 65
th minute Blackburn almost made it two, as first Olsson sprang highest to nod the ball onto Kuszczak’s post, before Ferdinand just diverted a cross beyond the far post. It was tense for United; so much so that Ferguson had already started pointing at his watch for added time at a Blackburn free-kick.
But within 10 minutes, United were on course for the title. A contentious penalty claim was given to United by referee Phil Dowd after Robinson had brought down Chicharito. There was definitely contact from the goalkeeper, but Hernandez had appeared to kick the ball out of play.
After a long consultation with the assistant referee, Dowd pointed to the spot and
Rooney dispatched the penalty to send the away fans into raptures and take United within touching distance of a record-breaking 19
th league title.
The next 10 minutes were full of keep-ball play from United, with Blackburn seemingly content to settle for a point. At one stage United kept hold of the ball for nearly two minutes without conceding possession.
In truth, the match might as well have ended in the 74
th minute, with United playing out the remaining time with consummate ease, with perhaps the least entertaining period of football of the season.
But United and their fans will care not, with Sir Alex Ferguson finally overtaking Liverpool’s long-standing record and cementing Manchester United's place as the most successful team in English league history.