Celtic dominated but only went ahead in the 56th minute after referee Steven McLean adjudged the Rovers defender to have fouled Commons inside the box.
The Scotland international slammed the ball into the corner of the net past Rovers goalkeeper David McGurn and the Irn-Bru First Division side's resistance was broken.
Late goals from substitute James Forrest, on for Tony Watt, and defender Charlie Mulgrew completed a solid afternoon's work by the Hoops.
Celtic manager Neil Lennon admitted the award "looked soft".
He said: "I didn't get a great view of it and I might agree with Simon.
"I haven't seen it again but it looked soft, but the referee was right there.
"But we could have had a penalty for handball in the first half, I have seen penalties given for a lot less.
"But the way Kris took the penalty pleased me, the game opened up and I thought we looked great in the last 20 minutes."
- Sports & Recreation
- Charlie Mulgrew
- James Forrest