The Red Devils have leaked goals at the start of the Barclays Premier League season, but picked up a much-needed clean sheet at the Sports Direct Arena.
Rooney told Sky Sports 1: "It's a great result. Everyone knows this is probably one of the hardest games of the season. We came here, defended brilliantly. We fully deserved the victory.
"The first six games of the season we haven't defended well enough - not just the back four, the whole team, and today we were brilliant against a physical team."