The Reds led 2-0 at the break courtesy of a superb volley by van Persie and a close-range finish by Welbeck and Rooney came off the bench to assist a thumping drive by the Dutchman and the England youngster's third goal in a week - a beautiful chip over Michel Vorm.
Van Persie, who hit both goals in the Community Shield victory against Wigan Athletic at Wembley, looks to be in the same formidable goalscoring form that he displayed in his debut season at Old Trafford.
"I think his foot was seven feet high in the air when he hit it [for the first goal]," commented Moyes. "It was great athleticism and a good pass by Ryan [Giggs] that got us in.
"But I was nearly as pleased by the goal Danny got. I like centre-forwards to score tap-ins inside the six-yard box. If you're ever going to get a lot of goals in the Premier League, you're going to have to get a few of those in the season so it's a good start for Danny. Obviously, he's got the fourth too, which he earned through his hard work throughout the game.
"I've been made very aware at this club about scoring goals and they tell me Danny only got one [league goal] last year so he's got two now. It's a start and if we can get everybody chipping in, it's great but it'll do Danny's confidence a lot of good. The goal he got against Scotland helped him, although I don't like saying that, and I'm pleased with his contribution."
Rooney came off the bench to make a positive impact and received a good reception from the