First you need to determine whether or not your ceiling has been painted before. Get a stool or step ladder that will allow you to run your fingers along the ceiling. Press firmly and move your hand across the surface. If it hurts, its been painted before. If it feels relatively soft and crumbs fall down from the ceiling, it has never been painted.
Second, the right paint is important. If your ceiling has never been painted, you absolutely must use an oil-based paint. If you don’t the stucco will turn to mud, start falling on your head, and your ceiling will end up looking uneven and patchy. If it has been painted before you can use any paint you like, preferably latex as it is easier to clean up and doesn’t smell as bad.
Third, the best roller to use is called a “split foam roller”. It is made of yellow foam and cut into little rings. This roller is really helpful if your ceiling has never been painted before as the little stucco peices don’t get all trapped up in the roller, but it is good for previousl painted ceilings as well. Don’t ever use one on flat ceilings, because it will leave lines. You can buy them at most big box stores, or your local paint store.
How much paint will you need? One gallon of oil-based paint will cover a typical 10′ x 10′ room as it soaks in a lot. If the ceiling has been painted before it will use quite a bit less, but you still need to buy a gallon. Hope this was helpful.