On the Adventure of the Seas, soft serve ice cream seemed to be everywhere for free (on the promenade, cafeteria, etc.). They do have Pizza at the Island Grill and a small shop on the Promenade. Pizza is available 24 hrs from Room Service. Note: they bring you a whole pizza, not just a slice. A friend ordered 5 slices for himself and his wife, and was surprized when they showed up with 5 complete pies!
Towels are at the pools and they discourage you from taking the towels from your room.