Twenty-four hours after signing a new four-year contract that media reports said was worth 300,000 pounds ($499,800) a week, the England forward repaid the faith of manager David Moyes with a stunning volley in the 68th minute.
Rooney's strike came six minutes after Robin van Persie had converted a penalty and secured a comfortable away win, their first of 2014, against a tough Palace side.
"Sometimes when Wayne doesn't have time to think he does things naturally," Moyes told a news conference after the champions rose one place in the table to sixth, 15 points behind leaders Chelsea F.C.
"He's got all that natural talent, the technique and the ability to get his weight behind the ball to strike it cleanly. He works hard for the team, some of his passing was fantastic tonight and his finish was great."
Rooney has made 431 appearances for Manchester United F.C., notching 209 goals. He is fourth on the club's scoring list and is eyeing Bobby Charlton's record of 249.
United were fresh from a warm-weather training break in Dubai and Moyes said a good result against Palace was needed ahead of the Champions League last-16 first leg at Olympiakos Piraeus of Greece.
"We have a big European tie on Tuesday and our focus goes on to that now," the Scot said. "We wanted to win today to go into the game in good form and with confidence - it's such a big game.
READY TO PERFORM
"We hadn't played for 10 days so I wanted to make sure all the players were ready to perform again on Tuesday."
Sixth from bottom Palace went into the match unbeaten in four games at Selhurst Park.
"It was most probably our best period just after halftime," said manager Tony Pulis. "The penalty was the changing point in the game and it took the pressure off United.
"Then we were chasing the game and against top teams that's very difficult. We've got to scrap and fight against every team we play against - today was disappointing."
Pulis said that playing just behind the striker, as Rooney did against Palace, was his most dangerous position.
"They've done well to retain him, he's a top player," he added. "Where he played today is his best position.
"He's got such a range of passing, he can kill you with a pass. He played well and scored a great goal."