Debutant Antonio Valencia played a major role in both goals as United's wingplay overpowered the visitors, who enjoyed their own opportunities in an open game littered with chances.
Michael Owen, also making his Old Trafford bow as a United player, was desperately unfortunate not to find himself on the scoresheet, as he passed up a pair of chances in each half.
While the finishing was off-key, there was much to admire in Owen's movement and, crucially, his link-up with England team-mate Rooney.
Fielded together for the first time at club level, it took under 20 minutes for the duo to click in devastating fashion. Rooney's superb slide-rule pass released Owen, who stabbed his effort neatly over Cesar Sanchez, but also just past the upright.
Rooney dragged perhaps an easier chance wide when he reached a cross from Ritchie De Laet, before Michel thundered a shot against Ben Foster's crossbar for the visitors.
Valencia used the interval to make 10 substitutions, and were quickly cursing that decision as Thiago Carleto limped off within minutes of his introduction. Substitute goalkeeper Miguel Angel Moya eventually replaced him, but by that point United had moved ahead.
Valencia, who had caught the eye more for his ceaseless hassling down the right flank before the break, sped past two defenders and curled in a superb