There are many of the cruise lines which will provide dietarily for coeliacs but very few who will actually guarantee it because of Tort Action. You must let cruise lines know your dietary requirements well before going on the ship. Someone might be able to tell you the best cruise lines from experience, but if you fancy a particular cruise put a reserve booking for it and then get your agent to check and confirm that they will cater for that condition before firming it up . ..... Neil.
Royal Caribbean do but as Neil says let them know with RCI it is firstname.lastname@example.org to request it
As Neil Down has already said many cruise lines will cater for Coeliacs, but you must let the cruise line know your dietary requirements when you book. When you board you will normally find a card in your cabin stating that the cruise line are aware that you have a dietary requirement. You will be invited to a meeting with the Head Chef to discuss your requirements. As a vegetarian, I have attended these meetings on Cunard, P&O and Fred Olsen, together with Coeliacs, Diabetics and passengers suffering from nut and egg allergies. In the case of Coeliacs, the Head Chef's were very obliging and able to provide, gluten free bread, cakes, biscuits for cheese, pasta, sauces and desserts. You would normally be given a special menu and asked to choose your meals for the following day. I work with a lady who is coeliac and I know the potential problems connected with cross contamination. She has travelled with Cunard and Fred Olsen and not had any problems. She had to ask the waiters for gluten free bread and toast at the buffet breakfasts as it is not put out on display. The waiting staff were keen to state that gluten free items are kept entirely separate from normal foodstuffs, although I'm sure they wouldn't guarantee that. My friend always takes an ample supply of rice cakes, just in case! Happy cruising, Jan .
I have only sailed P+O and they are excellent on gluten free at the sit down meals but less good at the buffets where getting a hot meal is rather difficult if not impossible.
I see the comment below about meeting the chef but that hasn't been my experience and I don't feel it has been necessary. The booking I make states I am gluten free and thats all they need and they look after me very well.