Argentine international Tevez is still to sign a permanent deal with the Champions League-winners after initially arriving on a two-year loan.
Sir Alex Ferguson is keen to get him on a long-term contract with Europe's top clubs sure to be monitoring the situation.
And Rooney is adamant that United should waste no time in securing his future.
"It is crucial to get him signed and I am sure that will happen," he said.
"Carlos loves playing football here, he's enjoying it so I don't see why it will be a problem."
Rooney believes much of the Reds' success this season is owed to Tevez, despite initial claims that he and the Argentine wouldn't be able to play together.
"We saw him at West Ham what a great player he was and how hard he works for the team," said the England international.
"I had no doubts that we could play together and from training with him when he first came you could immediately see the qualities he had. I couldn't wait to play with him.
"Towards the end of the season we didn't play together a lot, but when we did, we did really well.
"He's been brilliant. He's a battler, he works so hard and has scored 19 goals, which is brilliant."
Meanwhile, United manager Sir Alex Ferguson and his assistant Carlos Queiroz have been cleared of a charge of improper conduct by the Football Association.
The charge related to comments made following United's FA Cup defeat to Portsmouth on March 8.
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RoCarldo (29/05/2008 at 09:22)
There appears to be a lot going on with the signing of new contracts, Evra, Tevez etc....As we can't see the bigger picture of what is in the pipeline (only Fergie really knows) we'll just have to wait and see.
I wonder if Fergie is waiting in the shadows to see what's going to happen about all this REAL business, maybe that's why a few other contracts are being stalled.
(no idea, just thinking out loud here)