I did have one of those staterooms and there was very little motion, most of the time.
On our return to Port Canaveral, the Captain announced there would be high seas. Then it wasn't really rocking motion in the cabin. It felt like an endless elevator. Slowly up and then slowly down, all night. I took Meclizine as soon as the Captain made the announcement. I never felt sick and the motion was easy to sleep through.