The former Manchester United and England captain had a hand in two of DC's goals as they beat Vancouver Whitecaps 3-1 in their MLS encounter.
Following the win, Rooney stated he was there to keep winning and thanked the city of Washington DC for welcoming him to the club.
"My teammates might look at me as someone who has had a career with Manchester United, Everton and England and they haven't got to that level yet," Rooney told Sky Sports News. "But I am a DC United player now. And I want to win.
"It was a great victory. I thought we played some fantastic football. It was a big night for the club opening the stadium and it was important to get the win.
"It has been easy [to adjust] - I'm enjoying it. It was a great atmosphere. People in the city have given me a lot of freedom to be me, which hasn't always been the case.
"I was just as eager to get on the pitch as they were to see me on the pitch. They were great. I hope we can give them a few more wins."
DC United currently sit bottom of the MLS Eastern Conference.