Facing the media for the first time as a Major League Soccer player, the ex-England international said that he signed for the American outfit to "compete" and "embrace" a new culture.
"I'm not here to see out the last few years of my career. I'm here to compete. I'm here to win, and that's the way I've always played," he told reporters.
"I've always set high targets. I demand a lot from myself and I demand that from my teammates as well.
"I'm not coming in and looking to change things at DC United. I will adapt to the way the club is run and I will embrace that."
Rooney, who left Everton on a free transfer just one year after rejoining his boyhood club, is expected to make his DC debut against Vancouver on July 15.