Both players scored as United rallied from 3-1 down to claim an impressive win in Germany.
Rooney scored twice before turning provider for Kagawa to notch United's winning goal as they claimed a dramatic 4-3 victory.
The England forward said that he was delighted to link up with the creative former Borussia Dortmund man.
He told MUTV: "It was great to play with Kagawa, obviously he's a very clever player.
"The likes of him, Chicharito and Tom Cleverley are players who are capable of getting on the ball and linking the play and it worked well for us tonight."
United open their Premier League campaign away to Everton on Monday, August 20.