The striker's double was cancelled out by City's second half fightback, only for Robin van Persie's deflected free kick to take the Reds six points clear of the reigning champions, and Rooney admitted the Reds were raring to face their near neighbours after last season's dethronement.
"It's a great day for us, to go six points clear and beat our greatest rivals, especially after what happened last year," the striker told Sky Sports.
"We've waited a long time for this to happen and I'm sure everybody at the club, all the fans... we know how much it means to them and we're delighted. We're going to celebrate. They've had a great record here and to spoil that is a great feeling."
Rooney's clinical early double had the Reds coasting at half-time, but the Blues' now customary fightback had the game finely poised going into stoppage time.
Van Persie's injury-time free-kick swung the game decisively in United's favour, continuing this season's trend of running every single supporter through the wringer before settling on a happy ending.
"To be fair it's been like that all season," smiled Rooney. "To lose a two-goal lead... to be fair we were hanging on a little bit at the end. They had a couple of chances, but a bit of magic got us the three points."