Rollers

Rollers are the tools of choice when you have a large area to cover. Rollers will use more paint than a brush. Ceilings and interior/exterior walls can be covered with much less time and effort, but as with brushes, you must choose the correct type.
Rollers are also available in two categories:
Natural - Oil-based paints work best with natural materials, such as mohair or lambswool.
Synthetic — these rollers are made of nylon, polyester, or a combination. Use with water-based paints.
For latex paint, use synthetic materials only. Natural material is too absorbent to use with latex paint. Either synthetic or natural material can be used with oil-based or alkyd paints. It is always a good idea to check the manufacturers' recommendations before purchasing.
Nap (or pile) is the length of the roller's painting surface. Lengths will vary from 1/16" to 1 1/2". Choose the correct nap for the paint job. If you're painting a smooth surface, choose a short napped roller. For a rough surface such as masonry, use a longer nap. Rollers with textured surfaces are also available for special fashion finishes.
Rollers come in widths from 4 to 18 inches. The metal frame for the roller cover comes in two types — birdcage and metal. The birdcage frame works better if you're using fast-drying paints, as it cleans up more easily than the solid-metal type. Most handles are made for attaching an extension.
Trim rollers come in varying shapes and sizes. Cone-shaped types work well in inside corners. Doughnut-style rollers paint moldings and other fine work.
When purchasing a quality roller:
Look for beveled edges on the roller for a smooth finish.
Check to make sure the roller has no visible seams.
Give it a squeeze — it should rebound to its original shape.
Roller tips
Moisten before use with water or thinner to prevent paint from drying on the roller.
Load the roller with paint from the slanted edge of the tray to prevent overloading.
Paint in shape of the letter M. Start by moving the roller away from you. Without lifting the roller from the wall, fill in the open space.
Don't try to paint too quickly.
To clean a roller cover, roll it back and forth on newspaper. Remove paint with the proper thinner. If you're rinsing out solvent-based paint, wear rubber gloves. Let it dry before storing.
Disposable rollers are available. If you don't plan on repainting soon, you may want to use these to avoid cleanup (especially when using oil-based paint).