Tevez struck in the 87th minute in France as United claimed a 1-1 draw from the first leg of their Champions League last-16 tie.
Rooney told Sky Sports: "It is always crucial to get an away goal and 1-1 is a lot better than 1-0. It was a crucial goal to take back to Old Trafford.
"I felt we controlled the game for most of it. They had a few chances and stuck the ball in.
"Lyon are a good team and we know we have to concentrate 100 per cent."
United manager Sir Alex Ferguson admitted his side were caught out by Karim Benzema's opening goal but was pleased with their display.
Ferguson told Sky Sports: "I think we showed our determination to try to get back.
"We lost a goal out of nothing. We were in complete control and it knocked us back a bit.
"They defended very well and made it difficult for us but I think we deserved it without question.
"There was an urgency to get back in the game and I think we are best in that situation."