Rooney told MUTV: "It (the support) is brilliant. Some teams struggle to fill the away end in a Premier League match. Obviously we get more tickets in the Cup but we've filled it again.
United deserved their latest victory at Villa Park by virtue of being more clinical in front of goal. But Rooney believes the game could have gone either way until Cristiano Ronaldo finally drew first blood in the 81st minute.
"It was an even game and towards the end, it looked like going to a replay," said Rooney.
"We did well to keep going and Ronaldo did well to get in the box and put us in a winning position. We were so thankful to get the first goal because we knew then the game would open up a bit more for a few more chances."
When Rooney converted one of those chances, it took his tally for the season to 11 goals for club and country - not bad in a campaign blighted by breaks for injury and illness.
"It's been a stop-start season for me. But I'm looking forward to getting in a full week of training before the Newcastle game.
"Hopefully I'll be playing regularly again now and helping us to win trophies."
Rooney would certainly love the FA Cup to be on his list of trophies won, having lost his two finals so far in 2005 and 2007.
"Hopefully we can go all the way this time, it's a boyhood dream of mine to win the FA Cup."