The Manchester United forward missed the chance to earn a Champions League victory in northern Spain when he belted his second-half effort against a post.
It meant United had to settle for a goalless draw, which keeps them top of Group A but still leaves them needing a victory from one of their final two fixtures to guarantee a place in the last 16.
Van Persie has missed before, against Southampton last year, and Rooney, who also knows the pain of not converting from 12 yards, does not feel it will be a problem for the Dutchman.
"Of course [everyone misses from time to time]," said Rooney.
"Most forwards in the world miss penalties. That won't affect him, I'm sure."
With Van Persie also striking a post from Ashley Young's cross and Javier Hernandez inexplicably failing to convert after Shinji Kagawa provided him with a glorious six-yard opportunity, Rooney felt United had done enough to edge it.
"We're disappointed we didn't get the three points as we had the best chances," he said.
"Overall, however, we can see the positives. We got a clean sheet and we're still top of the group."
The incident that earned United their penalty has put Young back in the spotlight, though.
While referee Nicola Rizzoli booked Markel Bergara for the tackle, contact did appear to be minimal.
Young has been criticised for diving before and former United skipper Roy Keane was scathing in his analysis on ITV.
"Ashley Young has conned the referee," said the Irishman.
However, manager David Moyes adopted a more defensive tone.
"I have seen it and the boy certainly tugs him in the box," said the United boss.
"If you look the referee is two yards away from it and decided to give it.
"All I know is he got a penalty kick from a decision, I don't know anything about reputations or anything.
"The referee was there. He made quite a lot of decisions tonight and that one he gave a penalty kick."
Sociedad coach Jagoba Arrasate was less certain.
"I couldn't really see it from the dug-out," he said.
"The player kind of folds. I would need to see all the replays from the TV."
United will be without Marouane Fellaini when they visit Bayer Leverkusen in three weeks' time after the Belgian was sent off in stoppage time for two yellow card offences.
"As I said earlier regarding the penalty kick, the referee made decisions all night," said Moyes.
"He is the one who must have seen fit both to award a penalty and send a player off.
"I thought he made some strange decisions all night and that was another one of them."
Moyes did then accept he would probably be better off not discussing the performance of Rizzoli who, much to Sir Alex Ferguson's chagrin, sent Rafael off in a Champions League quarter-final against Bayern Munich at Old Trafford in 2010.
It took the heat off Hernandez, whose miss was inexplicable for a player of his undoubted class, who has scored three times in his last two games.
"The miss from Javier was an opportunity," said Moyes.
"To be fair to him the ball bobbled up. It just comes off the ground a little bit before it gets to him.
"But he gets in those positions week in, week out and that is where he gets his goals from."
Source: PA
Source: PA