Since the Mamba owners have not yet replied, I'll offer this. I recently made a somewhat similar change from a Dagger Redline to a LL Remix and had the same problem with my C-to-C. Worked with an instructor and made this adjustment: Before initiating the hip snap, I sweep out just a little bit further from the tuck than I had been. This solved the problem nicely for me.
Chris - The advice James gave is worth a try, especially if you do a c-to-c. I have paddled both the old and new Mamba and I haven't found the new Mamba harder to roll. What exactly is happening with your roll? Do you feel that the hip snap is not completing or is your head coming up? You could even post a video for me to look at your roll and I would be better able to give you good feedback.
James - the advice you gave is great! It is easier to come up more forward in a c-to-c with a more rounded hull. The Remix has more defined edges than a Redline. I've seen a lot of people try to come up too tucked forward in a c-to-c roll and it is challenging and not necessary. You have fine coverage if you come up parallel to your boat.