Rooney scored twice in front of a healthy 84,654 crowd, taking him to 31 international goals, one more than Alan Shearer, Nat Lofthouse and Tom Finney.
The result took England three points clear at the top of Group H and in good heart for Tuesday's crucial trip to Poland, even though Theo Walcott must be rated as extremely doubtful after being forced off inside the opening five minutes.
The visitors had a lucky escape in the opening minutes. Had Aldo Simoncini's airborne challenge on Walcott been executed by anyone other than a goalkeeper, it is difficult to imagine he would have stayed on the pitch - reckless and dangerous, it sent Walcott cartwheeling.
On the touchline, Roy Hodgson was furious. He was still seething when it was confirmed Walcott's evening was over and Aaron Lennon was sent on in his place.
It merely delayed the procession. Rooney had already come close on a couple of occasions when Oxlade-Chamberlain brought an excellent save out of Simoncini from the edge of the area.
Rooney then sent a far-post header from Tom Cleverley's cross narrowly wide before Michael Carrick smashed a shot against the bar, which Welbeck should have turned home but somehow shovelled against a post.
It was difficult to be too critical of England given the limitations of their opponents provided so little space to operate in. But their passing wasn't as crisp as it needed to be in order to open San Marino up and when the opener came, it was something of a surprise as Welbeck charged into the box and was upended by Simoncini.
Oxlade-Chamberlain completes scoring Rooney had no hesitation in accepting responsibility and duly drove home the spot-kick. Within three minutes, England had another. When Welbeck acrobatically turned home the winner against Sweden during UEFA EURO 2012, some questioned whether he meant it.
The impudent manner in which the 21-year-old turned home Lennon's cross, from a very similar position, left no room for debate. Rooney was denied by a brilliant Simoncini save before the break, then Carrick's shot was deflected away from danger immediately after it.
From the corner, Gary Cahill really should have scored but when Leighton Baines, who had kept his place at the expense of Ashley Cole, picked him out at the far post, the Chelsea man shinned it rather than catch the ball on the volley as he intended.
Cahill then sent a header wide before Baines was inches away from curling home a 25-yard free-kick. Hodgson decided to inject a bit more life into his midfield by introducing Jonjo Shelvey for his debut.
Lennon was about to get a free-kick when Rooney fired home from the edge of the area, a landmark goal which means he has only four more men to overtake and become England's greatest marksman.
Yet again, Welbeck followed up almost instantly. Once more at the near post, this time Cleverley providing the cross which he prodded home from close range.
Hodgson had seen enough to get Rooney off in readiness for Tuesday's more testing assignment with Poland in Warsaw. It meant he was only watching when Oxlade-Chamberlain made his own little bit of history 14 minutes from time, tucking himself behind Tommy Lawton, Michael Owen, and England's youngest goalscorer of all, Rooney.