They provide room service request cards in the desk drawer in your cabin for the purpose of pre-ordering items for a continental breakfast.
You circle the items and the quantity desired and the time (I think it's in 30 minutes increments from 7am until 9 something?) and you place the card on your outside door knob before 1 or 2am. Someone comes around and collects them during the night and they fill and deliver the requests very close to the requested time.
We always enjoy coffee, juice, and croissants in the morning when we're on a cruise, very tasty and enjoyable.
We haven't tried to order anything other than the continental breakfast at a particular time but they're usually very accomodating so I would imagine they could do it for you at other times too.
hope that helps