sinjin,

You don't say whether you have status with NW or if you are traveling Business or Economy, so this may or may not apply. My travel is almost exclusively Trans-Pacific. I have both a 22" and a 24" roll-on. (Samsonite) I always travel Business Class and both will fit in the overhead storage bin. I have never been confronted by an FA on NW. This might be due to my status (Platinum) or my WBC ticket.

-RKG