I remember thinking the same thing about the roll the first week. In fact, I remember sort of dreading getting in the car for a couple of days -- because of the motion sickness feeling. I never dared mention it to the kids or husband, tho; didn't want to put the thought in their heads.
I sort of blamed it on the tires, also, but to tell you the truth, it just went away. I had the tires rebalanced at the beginning of week 2, and whether it was psychological or not, the nausea seemed to disappear around the same time.
I no longer notice it...at all. It is a non-issue, and I'm the kind of person who does get carsick on winding roads, etc.
Hope that helps puts your mind at ease. I'd probably try to upgrade the tires, tho; these are crummy.