Last year's champion Shahjalal and runner-up Jibon Boli did not participate in this year's competition
Rooney, who went back to his boyhood club in July after 13 years with United in which time he scored a club-record 253 goals, wasted two good chances to cancel out Antonio Valencia’s stunning early strike for the hosts.
He was substituted late on and then watched United add three more goals through Henrikh Mkhitaryan, former Everton striker Romelu Lukaku and Anthony Martial.
A rather flattering victory lifted United level at the top with Manchester City. Both sides have 13 points from five games and have scored and conceded the same amount of goals.