Nevertheless, Celtic ended up making light work of their opponents, Dembele rattling home a penalty and James Forrest adding a third for a 3-0 win on the night and a 6-0 aggregate triumph.
"It was a very good victory considering we were down to 10 men," Rodgers told BBC Sport.
"Defensively, we pressed the game very well and going forward we created opportunities.
"We got three goals and could have had a few more. We dominated the game with 10 men."
Celtic, who will be monitoring Dembele's fitness after the forward suffered a "little tightness in his hamstring" late on, will face Rosenborg in the second qualifying round.