My kids got pretty good at hitting that button on our 10 day cruise. DS in particular had them bring him a bowl of potato chips, and 2 whole milks late most afternoons. He'd usually take them to the movie with him. I just put a stack of bills in the desk drawer and told them to tip the server.
The room service menu is somewhat limited. If you're in conceirge (cats 1-3) you can get a full menu of room service. We didn't usually do breakfast. Instead, I'd head up to the buffet and bring back a tray for everyone to pick off of.
Lunch/evening, they had:
pizza
cheese and cracker platter
several sandwich/chip combos (PBJ, club, ham/cheese, turkey as I remember)
chicken noodle soup
chili
cookies
fresh fruit bowl (which was things like whole bananas, apples, etc., not CUT fruit)
Enjoy!