My Sentry CT only leaks at the front bulkhead mostly when spraying the debris that gathers in that open recess. I haven’t bothered to do a water test to correct it since I have no need for 100% water tightness. I would remove the rails and make sure the foam strip is intact. Possibly tightening the clamps or adding a thicker closed cell foam strip. Try customer service for their advice.
I would investigate the seals and add more only on the inboard side, so that any intrusion will stay out. I would use a very thin seal because a thicker one will actually raise it and cause more issues than it solves.
I would not expect a hard roll-up to be as water resistant as a hard tri-fold because it has so many segments. As it wears, especially if you have it rolled open a lot, the fit is going to get looser.
Yes, the leaks are frustrating; I've put black silicone putty in the bedrail gap that's about 7 inches behind the cab on the bedrail. I even added some more yesterday; it's a headache to try to get it to stop leaking. But persistence will pay off. My Sentry CT came with the rubber pads on the front of the siderails misaligned, so I had to re-position them to close the 1/8" gap along the bulkhead. And the "L" shaped weatherstripping included needs to go on first on the bulkhead, but if you follow the enclosed directions, it says to put that on after the siderails which makes it not line up properly.
This video is from RealTruck.com and it helps address the leaking issue; it's an aggravating problem but I've used black silicone putty in the bedrail gap and waiting for the next rain to see if my touchups yesterday are going to solve the problem