The Dutch boss, who announced his retirement from football earlier this month, led the Red Devils to the FA Cup during two seasons in charge between 2014 and 2016.
Rooney, who played under United legend Ferguson for nine years, praised the former Barcelona and Bayern Munich manager as the most tactically astute figure he has worked with.
“He (Van Gaal) was tactically the best I have worked with – in terms of setting you up in a shape defensively and everyone knowing their roles,” Rooney told talkSPORT.
“It was just about getting the attacking side right as well as the defensive side.
“He won a few trophies but it didn’t pan out the way everyone would have hoped.”
Rooney joined MLS outfit DC United last summer and has started the 2019 season in sparkling form, scoring a hat-trick in a 5-0 win over Salt Lake last wekend.
