For a few precious seconds following the final whistle at Sunderland, United thought they had retained their crown and secured a 20th league championship, only for their dreams to be dashed by Sergio Aguero's stoppage-time winner for Manchester City.
It left United on 89 points, but condemned to runners-up spot on goal difference. Already Rooney is looking ahead to next season and the chance to reclaim the title.
"Yesterday [Sunday] was a difficult day for everyone. One minute you think we have won the title, then we haven't, which was heartbreaking," the 26-year-old told MUTV at the annual Manchester United Player of the Year awards.
"That is how it goes sometimes. We have to believe in ourselves.
"We have to look forward to next season and hopefully we can win some trophies next season. I am sure we will be back. We all believe in ourselves."
Rooney has no doubt where it all went wrong for the Red Devils as they tossed away an eight-point lead with just six games remaining.
"The biggest disappointment was the Everton game," he said.
"To be 4-2 up, with 10 minutes to go and to lose that lead is disappointing.
"But there are a lot of young players in the team. That is only going to benefit them. They will learn from that."
That view was shared by central defender Rio Ferdinand.
"Yesterday [Sunday] was a crazy day of emotions," he said.
"I thought we had almost bagged it but then the impossible happened.
"We have to dust ourselves down and make sure we are in the right frame of mind.
"We have experienced players in the squad. We all have to learn and be stronger. You have to be together during the good times and the bad."
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Sir Alex Ferguson later took to the stage to confirm Antonio Valencia had won the Players' Player of the Year award.
In fact, it proved to be a superb night on a personal front for Valencia, who was also crowned fans' Player of the Year, in addition to the goal of the season for his effort at Blackburn last month.