On those cruise lines that charge the daily/weekly fee (I think you still have to actually request that on Royal Caribbean), it covers the dining team and cabin steward. Extra tips to these crew aren't necessary unless you feel like it, but they aren't expected. Room service should get a tip, and since we take our kids, we tip the camp counsellors that spend a lot of time with our kids.

Drinks have tips added to them automatically, so no need to tip bartenders or drink servers unless you really feel by the end of the cruise that a particular person gave you over and above service.