Bukayo Saka's first-half tap-in was enough to secure the Gunners a place in the competition's final, sparking scenes of pandemonium.
Speaking after the game, United legend Rooney was struck by how incredible the atmosphere was inside the Emirates, and claimed it was even better than the last time he played in North London for a Champions League semi-final.
“I played a Champions League semi-final here for Man United and the atmosphere that evening was nowhere near what it was today," Rooney admitted.
"Mikel Arteta and the board deserve credit. It’s Arsenal’s year, I think.”
Rooney, of course, is referencing the time when his Manchester United side beat Arsenal 3-1 at the Emirates in the 2009 Champions League semi-final.
The Red Devils then suffered a 2-0 defeat to an imperious Barcelona side, the same fate the Gunners will hope to avoid on Saturday May 30 when they will play either Bayern Munich or Paris-Saint Germain.