The right paint roller for your project depends on the type of paint you're using, the surface you're painting, and the desired finish. For smooth surfaces, opt for a short nap roller (1/4 inch or less). For rough surfaces or textured walls, use a longer nap roller (1/2 inch or more). For oil-based paints, choose a natural fiber roller, such as mohair or wool. For water-based paints, use a synthetic fiber roller, such as nylon or polyester.