Remove furniture from the room, and place it in a safe location. Cover the floor, as well as items too large to remove, with a drop cloth. This will prevent damage to your furniture from the bleach solution.
Put on a pair of rubber gloves and old clothing, and open the windows in the room where you'll be working.
Pour 2 gallons of lukewarm water in a clean bucket. Add 1 1/2 cups bleach to the water, and stir for several seconds with a wooden spoon. For colored ceilings, use oxygen bleach instead of chlorine bleach.
Attach a clean paint roller to the roller handle. Screw an extension handle into the paint-roller handle. Pour the bleach solution carefully into a paint tray.
Roll the paint roller in the bleach solution until it is saturated. Hold the roller over the paint tray for several seconds, and let the excess solution drip off the roller and into the tray.
Start at one corner of the ceiling, and begin applying the bleach solution over the ceiling. Roll the roller in a back-and-forth motion across the ceiling while making your way to the other end of the ceiling. Wait 15 to 20 minutes before continuing with the remaining steps
Attach a clean paint roller to the roller handle. Saturate the roller in cool water, and rinse the bleach solution off the ceiling the same way you applied the bleach solution. Let the ceiling dry.