If Rooney showed no sign of nerves as he thumped his spot-kick past Rovers keeper Paul Robinson, who had brought down Javier Hernandez to concede the penalty, afterwards he admitted he had been "terrified" before taking his kick.
"I just had to compose myself, said Rooney. "After the year I've had, you know the ups and downs," he added, referring to the transfer request he submitted earlier in the season.
United manager Sir Alex Ferguson added: "Our away form has not been great, yet our home form has been absolutely fantastic - that's won us the title."
FA Cup win a bonus - Roberto Mancini
The Red Devils have dropped only two points at Old Trafford, though Ferguson's side have picked up 25 points from a possible 57 on their travels.
United will be presented with the Premier League trophy on 22 May after their home game at against relegation-threatened Blackpool, who boosted their hopes of survival with a 4-3 win over Bolton on Saturday.
As Mancunians celebrated both in the city, Blackburn and London, Manchester City Council confirmed that Blues' victory parade would take place on 23 May.
United's parade celebrations will be held on 30 May - two days after Sir Alex Ferguson's side face Barcelona in the Champions League final at Wembley.
While Manchester's two set of fans revelled in their respective successes, Mancini insisted his players would not be drinking to toast their FA Cup win.
"No, they know that we should play in three days" said Mancini, referring to City's Premier League game against Stoke on Tuesday at Eastlands. "We have another two games and we want to try if possible to get third position."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.