United will have a new skipper to appoint for next season with defender Nemanja Vidic having already agreed a free transfer to Inter Milan.
There may also be a vacancy with England if Steven Gerrard, 33, decides to call it a day at international level after the World Cup.
Rooney told club magazine Inside United: "I've done it a few times and, if the manager wants me to be the captain, I would have no problem with that. I would take it with both hands.
"However, it is down to the manager, because it's his decision on whoever he feels is the right person to lead the team. I'm sure he'll make that decision when the time comes.
"I think, whether you've got the armband or not, I always feel I'm quite vocal on the pitch. I try to help the players when I feel I can and say what I think. I believe that's the most important thing."
In terms of England, the 28-year-old, who signed a new five-and-a-half-year contract with United last month, said it would be "an honour" to succeed Gerrard.
He added: "You don't know what Steven is going to do in the summer, only he knows.
"It would be a great honour to captain my country but, again, it's the manager's call and I'm sure he'll have a few contenders."
Rooney also admitted it is agony to see United's deadly rivals Liverpool and Manchester City fight it out for the Barclays Premier League title while David Moyes' side are facing the prospect of missing out on the Champions League.
The United striker also said that he and the other players have to take responsibility for the club's struggles this season because they "haven't been good enough".
United face Liverpool at Old Trafford on Sunday knowing that defeat would be another stunning blow in a painful season.
He said: "To see City doing well, and particularly Liverpool, is really difficult.
"It's not nice when we know we are capable of being up there challenging and we haven't been doing that this season.
"However, it means we have to step up and get back up there because the feeling we've had this season is not a nice feeling at all to have.
"As a group of players and a team we haven't been good enough this season and we have to put that right.
"After Sir Alex being here for 26 years, there was always going to be a change whoever came in and, in fairness, I think the players have to do better.
"Hopefully we can make the top four but, if not, we will still come back firing for next season."
Rooney also revealed he has been staying behind after training to help teenage winger Adnan Januzaj.
He said: "I've stayed out after training with Adnan a few times. Even just working on free-kicks and crossing. It actually benefits me as well and it benefits him.
"I am trying to help him get better and better, which I feel he is doing, and I think young players need to practise all the time, especially coming into the side. Senior players also need to keep practising to stay on top of their game so it works for both of us."