React to the roll and either punish the ending lag or punish them with your good position (grab if they shield, Dsmash if you think they'll spotdodge, space ftilt if unsure etc).
If you can't do that, it is probably because you're over committing (like throwing out smashes) and it is allowing them to roll safely. They might also be rolling under a prediction that you'll commit to something.
Rolls in general are probably not your problem. For example, one thing I do often is when a Marth is below me, and I'm in my shield, I know they want to F-smash me. If I shield drop, fast fall, and start a roll, by the time they react to me shield dropping, and try to F-smash, my roll has started. If I'm successful, I get a free Dsmash.
Edit: Just watched some of your match. You didn't seem to be throwing out smashes or generally committing too often. Maybe you were tired or something? After a long period of smash I sometimes get lazy and start throwing out smashes, then lose momentum, start losing when I shouldn't, and it creates a cycle.
Your Shiek seemed pretty solid btw. (From what I saw)