I agree with Bill. I always keep a handful of one dollar bills loose in the safe so that they are easy to get to. The room service guys really appreciate a small gratuity. Keep in mind... there's not many people who will bring you food while you're in your underwear. (grins)
Star Princess - 2005; Caribbean Princess - 2004;Golden Princess - 2003;
Grand Princess - 2002, 2001, 2000; Sun Princess - 1998;
Regal Princess - 1996; Star Princess - 1995
Yes, totally agree with the other posters about a few dollars tip, depending on the size of the order. If you have room service for breakfast, you can fill out the form the evening before and use that as a wake-up call, they usually call right before they bring up the food, works very well!
Just got back from the Grand Princess Western Carribean and I asked the Purser this same question. He said the tip is included. About 50 cents per person per day is the 10 dollar amount--seems like a small amount for such great service. We decided to tip for everything outside of the morning coffee delivery.