Welcome.
Flip through a few pages of the general Movement section and you'll find over a dozen threads on rolls, including a sticky thread. There's a lot of good advice to be had. The condensed version is that you may have to modify the roll and your body positioning slightly. We all have different postures, torso-lengths, widths, bone structures, etc. Perhaps the best thing you can do is get down on the ground and wiggle around to see what position your body requires.