I can't answer exactly for the Voyager but all the RCI ships I have been on, including transatlantic runs, have had their really good windjammer self service area open and the waiter service restaurants as well. The restaurants are open on sea days for breakfast and lunch the exceptions being that they often shut when in port and for breakfast on debarkation day when the Windjammer only is used. I would however not have the pasta dishes in the restaurant as I have found that they are served from a hot plate area in the restaurant itself and are invariably past their prime. For really good pasta visit the pasta station in the Windjammer.....hope that helps...Nei.
Sorry I forgot. Tea and coffee are there in abundance in the restaurant, Windjammer, served to your cabin and in the coffee cafe. Coffee is better than the tea but it's an American ship and it is available 24/7.....Nei.
On Voyager there will be waiter service in the main dining room, there is also waiter service of a different sort in Johnny Rockets American diner - well worth it for a bit of a 'show' and a darned good burger.