Well buddy, what can I tell you? I know with the old foam rollers, that this used to happen. The foam would compress over time and would form a channel.
With the new "Dura" rollers, no one has mentioned this. If you are squeezing hard enough to deform Neoprene rollers, then you must have Popeye forearms.

Oh...What type of lube are you using? Petroleum based lubes will soften rubber and eventually rot the rollers. Clean your device after every use with soap and water, this is also imperative for sanatiry reasons. Then put a drop of light oil at the hinges.