I agree about bringing the "good" earplugs. These are the soft ones that don't hurt your ears. And to make them even better roll them tight between your fingers, stuff them in as far as you possibly can, then make sure you have a small pair of needle nose pliers to pull them out in the morning if the string attached to them breaks ! Hopefully your room mate will not wear earplugs so they can wake you if the fire alarm goes off. Another smart thing to bring is a little headlamp if you have to get up for "nature calls" in the middle of the night without bothering your mate by turning on any lights in the room.
I'm not looking to cruise right now, so you have not heard much from me, but I'm still dreaming of the Pride of America cruise around HI with several extra days on land before or after.