If it has been painted before it no different than painting a smooth ceiling, just use a good ceiling paint and at least a 3/4 inch nap roller. If it has not been painted the best way is to spray it to keep the texture from raining down on you but that is not always practical and best left to a proffesional painter. It can be rolled but you take the chance of a little or alot of texture coming off.

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If you roll it, make sure the paint is thin, so it doesn't act like glue on the roller.