I have to disagree with Paul on where the cash goes when you give it to the Room Service waiter. I have spoken with two Hotel Directors, one on Carnival and the other on Holland America, and both said that as long as you have not removed yourself from automatic tipping the person you give cash to can keep it. If you did remove yourself from the automatic tipping program then that person is required to put the cash in "the pool". It is quite possible that Royal Caribbean, and its cruise lines, have a different rule.
What irritates me is that since the introduction of automatic tipping people feel they are "required" to give extra tips in order to receive good service. This myth has been propagated by online message boards, even this one, untruths spoken by cruise personnel looking to get more money, the passenger's feeling that the person deserves more money and someone's wish to feel like a big shot.
Many people now feel they are doing the wrong thing or are "cheap" if they don't give extra money to their wait staff, steward or room service. This attitude is creating a second level of gratuities and additional compensation for the service staff. If I was the service staff I would like this "extra" to continue.
If you don't give extra you are not at all cheap.
Having said all that I will say that I will give a room service waiter a couple of bucks if they lug a tray from the dining room, up a few decks, down a long corridor and deliver it to my door. I will also give a room steward extra if they do something, I request, that is outside the normal scope of their duties.