How to avoid getting rolled

Hey all. If any of you remember my first topic, I was worried about making the varsity team, I made it and am 4-1 now. My latest match at 135, was my toughest one this year, I won thankfully. I controlled him and could get easy take downs and he didn't really have any control on me from top position, I got a few escapes. My problem was that he would roll me when I had him on his back. I was winning 11-3 and had him on his back again, he locked my body and arched and flipped me, he did that about 4 times, how do I stop him from doing this when I see him at conference?

Get out to one side, and pick up his head. Can't get the bridge high enough to roll you if you pick up his head.