New strike partnership Clayton Donaldson and Farid El Alagui both bagged a brace, while centre-back Harlee Dean got in on the act with a late header.
Alex, who were forced to hit the ball long on a rain soaked surface, could only manage an second half consolation through Mathias Pogba.
Rosler said: "The first 35 minutes was the best 35 minutes I've seen since I've been here.
"We pressed them as a team, moved the ball well and were clinical in front of goal.
"It's difficult to pick anyone out after a performance like that, but I thought Kevin O'Connor was outstanding. He's a model pro who knows his job, does it efficiently and allows the other lads to play."