Rooney was back to his best as he ran the German side’s defence ragged and bagged his third Champions League goal of the season to round of his performance, much to the delight of his team-mates.
"I am not surprised at what Wayne is doing," said Giggs.
"The top players perform when the trophies are about to be handed out. They produce moments of inspiration when it matters.
"Wayne has done that time and time again over the years, so it was hardly a shock he was superb against Schalke."
The Welsh winger believes United are in a great shape as the climax of the season approaches and is hopeful of another good performance to all but seal the Premier League title against Arsenal on Sunday.
"This is what you want," he said. "The idea is to be playing big game after big game at this stage of the season because it means you are amongst the big trophies and going for the league.
"In that sense, we have got it exactly right. There are no issues. We have the squad to cope.
"I am sure the manager will make changes on Sunday but I also know the players who come in will be in good form.
"Hopefully we can get as good as a result and put on as good a performance as we did against Schalke."
Giggs is confident of progressing to the Champions League but has warned that Schalke must not be taken lightly despite United’s commanding position.
"Obviously we are massive favourites," he said.
"We have scored two away goals and we still have to play them at Old Trafford.
"But we have to be wary. Teams have underestimated Schalke before. We won't be doing that."