Rooney followed up from his brace against Milan in midweek to score another two, before Dimitar Berbatov capped a fine performance with a goal of his own in the final minute.
In truth, it was no more than United deserved as they dominated large parts of the game, both in terms of possession and territorial advantage. However, despite spending most of the game struggling to get out of their own half, Fulham did have chances at important stages of the game.
With the score still at 0-0, Danny Murphy picked out Bobby Zamora beyond the United defence, but the Fulham man opted to shoot first time and his volley was just too heavy to go over Edwin van der Sar and drop under the crossbar.
It was Zamora again, who found himself through on goal, when just one goal behind, but he didn't get the ball out of his feet quickly and Nemanja Vidic recovered to make a saving tackle.
The best chance of the first half came as a result of some clever passing between Berbatov and Darren Fletcher. The Scotsman found himself one-on-one with Mark Schwarzer, but he squared the ball for Rooney instead of shooting and Kelly just did enough to put the United man off and prevent him from scoring.
However, United managed to take the lead in the opening stages of the second half and it was inevitable that it should be Rooney who would fire them ahead. The United striker played it wide for Nani on the left. The Portuguese winger played the ball back into the path of Rooney and he side-footed calmly into the far corner from 12 yards. It wasn't the cleanest of strikes from the England man, but everything he touches at the moment just seems to turn to goals.
With just seven minutes remaining United eased clear. Rooney was the scorer, but Berbatov this time deserved all of the credit. He did well to beat two defenders down the right, but playing it low into the path of Rooney, who made no mistake with the finish low to Schwarzer's right from 10 yards.
There was still time for Berbatov to notch up his 6th goal in eight games in the final minute. Rooney played a delightful cross-field ball to Park, who brought the ball down well before crossing to the near post where Berbatov stooped to head home from six yards.