I'm going on a cruise in December and the ships are not included in roam like home. The postpayment for text messages is 0.75$/msg. Do the messages that are received from other people cost .75 as well as the ones sent?
I'm on PAYGo and when roaming in Spain or France, the incoming texts were $0.30, while outgoing were $0.75. The charges may depend on your plan and location so you may have to visit the website and find out how much Rogers charges under your specific plan for roaming texts. I don't know what "location" a cruise ship uses - you may need to contact your travel agent... Some cruise ships can charge exorbitant amounts for cell phone (or even internet) services.
You could also try PMing the moderators here with your information and they may be able to provide you with an answer.