Buoyed by news of the Gunners’ 2-2 draw at Birmingham earlier in the day, the Reds dominated from start to finish to record their second convincing win over Newcastle in as many months.
Ronaldo set up Rooney for the opener before the Portugal winger bagged his 28th and 29th goals of the season to put United out of sight.
Abdoulaye Faye pulled one back but Rooney’s superb second and a late strike from substitute Louis Saha left Newcastle still searching for their first win since Kevin Keegan returned to the club.
Reds boss Sir Alex Ferguson, mindful of the need to keep his squad fresh as they chase three trophies, made four changes to his starting line-up after the midweek draw in Lyon.
In came Nani, Darren Fletcher, Michael Carrick and Carlos Tevez for Anderson, Paul Scholes, Owen Hargreaves and Ryan Giggs, with the latter two not even on the bench.
Keegan’s men had conceded 11 goals in four games coming into the match and United threatened to open them up at will early on.
Carrick made a marauding run through the middle and played in Rooney on the right of the box, but the striker failed to pick out one of his team-mates with his pulled-back cross.