The England striker, 26, suffered a deep gash to his thigh in the 3-2 win over Fulham in August that left blood gushing from the wound and needed hospital treatment.
Rooney was sidelined for a month, missing four matches, while the injury healed, but he returned with a 76-minute appearance as Sir Alex Ferguson's side earned a fourth round trip to Chelsea with a victory against Alan Pardew's side at Old Trafford on Wednesday.
Now Ferguson must decide whether to break up the partnership of Robin van Persie and Shinji Kagawa to include Rooney in Saturday's Premier League match against Tottenham at Old Trafford.
But Rooney, who also missed two England internationals, was just pleased to have returned to United colours.
"Of course it was good to be back. It has been four weeks since I last played and I was delighted to be back out on the pitch playing," he said.
"It was a good run-out so I'm delighted and hopefully there are a lot more games to come.
"I feel good. It was my first game back after a few weeks and it was great to get the minutes under my belt and hopefully that will benefit me.
"It's great team spirit at this place and we're in a good place at the moment. Hopefully we can kick on after the good games we've had over the last few weeks."
Ferguson selected a youthful team against Newcastle, giving first starts to defenders Marnick Vermijl, Scott Wotton and Michael Keane, while Ryan Tunnicliffe and Robert Brady came off the bench for their debuts.
Darren Fletcher, who had a 10-minute appearance in the 1-0 Champions League victory over Galatasary last week, made his first start in 10 months after taking a break from football due to a chronic bowel condition.
The midfielder was watched by Scotland manager Craig Levein and was pleased to come through 90 minutes as he continues to work his way back to full fitness.
"It's great to be back," he said. "It's been a long time, so it's good to be back, especially at Old Trafford in a winning team.
"The back four were fantastic and they were talking to me the whole game and for two young centre-halves (Wotton and Keane) playing against two good strikers they were fantastic. All of the lads were."
Ferguson has promised that he will continue to use plenty of youngsters in future rounds of the competition, but he was also satisfied with the performances of senior stars Rooney and Fletcher.
"Both of them were excellent," he said. "Wayne tired before the end but that was to be expected but we're very pleased.
"They've done really well and I'm pleased with the win. The name of the game here is to win football matches and we've given our squad players and a lot of younger players a game. If they progress they'll be involved."
Anderson opened the scoring before the break and Tom Cleverley scored his first for the club before Papiss Demba Cisse pulled one back for Newcastle.
Despite the defeat, Magpies manager Alan Pardew believes his team now have the squad options to mount a sustained push for a Champions League place after finishing fifth last season.
"We had a strong finish last season but our depth is stronger now," Pardew said. "It was difficult to improve on that starting eleven but we didn't have the strength in depth every week and it cost us.
"Now the group is stronger and if we lose someone we can replace them like for like. That is important in the Premier League."