Paint rollers are essential tools in a painter's arsenal. They speed up the process and make it easier on the painter since one swipe with a roller is equivalent to multiple strokes with a brush. Rollers also produce a smoother, more uniform finished surface while using less paint. Using both rollers and brushes allows you to complete your painting job quickly and with great results.
Rollers are available in sizes from 2" to 18", with most falling into the 7" to 12" range. To achieve the best results, you'll want to match the size of roller to the size of your project. A small roller is good for drawer fronts and similar small, flat areas, while a larger roller is better for walls and ceilings.
Roller covers hold the paint and spread it on the wall or other surface. They come in different naps (or thicknesses) for different surfaces. It's important to match the nap to the type of surface you're painting. The smoother the surface, the thinner the nap.
You'll also want to match the cover's material to the type of paint you're using.