Paint rollers come in a number of sizes and materials.
Rollers typically comprise a handle and frame plus replaceable sleaves.
Professional rollers tend to have a deeper pile and are wider.
Pile rollers enable you to take a large amount paint to the wall and achieve a good coverage with emulsion.
Foam rollers are typically of the 4” type and used for painting gloss etc on to woodwork.
Rollers with relief patterns on them are for use with textured paints.
For the professional decorator a roller will usually be dedicated to each of the most common emulsions such as white and magnolia.
When it comes to cleaning a roller it is alarming how much paint is held in a roller. Washing with water rarely gets a roller truly clean and rollers that have applied dark paints will always present the risk of discolouring lighter paints used later.
A useful tool for getting paint out of a roller is the Harris Roller Cleaner.