The only surprise was in the scoreline. United should have at least trebled their tally, although a double figure winning margin would not have flattered the Red Devilss.
United were in a different class from the Geordies in every area of the field with the possible exception of goalkeeper - Edwin Van der Sar having only one shot to save while Newcastle's Shay Given was forced to make a string of fine stops.
Head and shoulders above everyone else was the magnificent Rooney.
He scored twice, hit the post once and should have had at least two other goals, while also setting up countless chances for his team-mates.
The first Rooney goal came in the eighth minute.
It was served up to the England striker on a plate by Newcastle right-back Peter Ramage, whose sloppy back pass from the wing landed perfectly for Rooney.
Given raced off his line to meet the United man, who almost nonchalantly scooped his right-foot chip over the Irish international goalkeeper and into the far corner of the net from 20 yards.
Rooney's second goal four minutes later came from a much better build-up.
Defender John O'Shea, playing out of his skin in midfield, started the move with a pass to Cristiano Ronaldo.
The Portuguese winger returned the ball with a cheeky back heel and O'Shea worked a neat one-two with Louis Saha before feeding Rooney who scooped the ball around Ramage and into the net from the edge of the Newcastle box.
Rooney was to go close on three more occasions - two blistering shots which past inches over the bar and a 68th minute chance when he hit the post.
That came courtesy of Newcastle's defensive confusion in the centre circle. Rooney raced clear of the debris, rounded Given in the Newcastle box, but clipped his shot against the post.
While Rooney should have had more goals, Ronaldo, Saha, Ji-Sung Park and substitute Ruud van Nistelrooy should also have been on the scoresheet.
Saha squandered a series of good openings, twice shooting wide when it seemed easier to score and losing control of the ball when through on a one-to-one with Given.
Park was twice denied by Given - the best save the Irishman's 79th minute acrobatic effort to claw away the South Korean's ferocious 20-yard effort.
Van Nistelrooy, a 74th minute replacement for Ronaldo, was put clear following good work by Ryan Giggs and Saha seven minutes later, but shot wide from close range.
Newcastle improved in the second half, after Lee Bowyer replaced Shola Ameobi, but could still only muster one real chance.
That came in the 55th minute when Emre set up Bowyer, whose 30-yard shot was turned behind at full stretch by Van der Sar.