United came into this game on the back of a poor run of form that has seen them drop 11 points behind the Champions League places but with Rooney having signed a huge new contract the day before. Crystal Palace have been on a good run, especially at home, but they never really looked like causing another shock.
David Moyes fielded his 'Fantastic Four' of Juan Mata, Adnan Januzaj, Robin van Persie and Rooney but, despite some good moments, they still struggled to make the breakthrough. The best chance of a frustrating first half fell to Marouane Fellaini after superb work from Mata but the Belgian placed his effort wide from ten yards when he looked certain to score.
Palace started the second half well but they couldn't really test David de Gea and they were soon to pay the price for all their hard pressing.
On the hour mark, Patrice Evra drove forward to latch onto an Adnan Januzaj pass before being brought crashing to the ground by Marouane Chamakh and referee Michael Oliver pointed to the spot. Van Persie stepped up and sent Julian Speroni the wrong way from the spot and Palace suddenly had a long half hour ahead of them.
Fellaini went close with a long-range drive just moments later as United looked to capitalise on the increased space. The icing on the cake arrived on 69 minutes as Evra reached the byline and cut back for Rooney to open up his body fire a rising half-volley into the top corner of the net.
Van Persie then struck the bar as the visitors threatened to run riot but that was to be the end of the scoring. Palace worked hard in the closing minutes to try and force a frantic finish but de Gea made a superb save from Yanick Bolasie to keep the hosts at bay.
United will hope that the win marks a turning point for them in their pursuit of a Champions League spot while Palace will just be grateful that they haven't really lost any ground in the relegation battle.