When choosing a roller, pick a small roller about 3 inches long. The roller should not be a foam roller but instead should have a cloth or fabric covering with medium-length nap. These rollers are not as heavy when rolling plaster onto the wall's surface. Once complete with your plaster project, rinse the rollers with water and allow them to dry for your next paint project.
Moisten your roller by running it under water. Stick the roller into the bucket of joint compound, and pick up plaster. The roller will not pick up much plaster at first, but as more plaster sticks to the roller, more plaster will attach to your paint tool. Take the roller and apply the plaster onto the wall by rolling in random directions. Peaks will form as the plaster is rolled onto the wall. Use the edge of a trowel to knock down the peaks of the texture for a smoother finish.
Keep more than one roller on hand and a pair of helping hands. Applying the plaster with a roller takes time. The rollers will become saturated with plaster, and extra rollers are often necessary. Ask friends or family to help roll on plaster. The project takes several days when attempting to roll on plaster in an entire room.
After your plaster has been rolled on, knocked down with a trowel and dried for about 24 hours, it may be ready to paint. Touch the plaster with your bare hand. If it feels cold or damp when you touch it, the inner layers of the plaster may not be dry yet. Wait an additional day. In humid situations, joint compound may take more than one day to dry.