If you are really sensitive to motion, then close to the waterline, middle of the ship (length and width) is the place to go from what I heard (makes sense). Yes, you will feel the rolls the higher up you go and the pitching too.

Ship size matters too. I was high up on a large ship (100-120' above waterline) on TPAC 10 months ago (ship was as long as RCCI's largest ships and only slightly less abeam). No stabilisers on the ship so when the roll was 15 degrees (either way from center), you'd be flying through the air some 20+' (calculated by trigonometry) which makes it difficult to sleep.