There are basically 4 different types of rollers that are used on garage doors. All rollers are made with steel stems with wheels at one end of roller. The difference is in the wheel itself. You have either plastic, steel or poly wheels. Plastic wheels are fitted at one end of roller stem and do not use ball bearings in their construction. Steel wheels come 2 ways, with ball bearings and without ball bearings. The poly constructed wheels are pretty much identical to a skateboard wheel or roller blade wheel. They are also made of the same poly material and always have a ball bearing system built in. If your rollers are constructed with ball bearings than they will be visible and need lubrication at least once a year.

Where can you find garage door rollers, what will the cost be?

Garage door rollers can be found in most retail hardware stores. They are sold individually at hardware stores and local garage door companies buy them in bags of 10 or more. Individual rollers cost about $5 each. A bag of 10 will cost about $30 to $40 a bag retail. If you buy them from a hardware store than you are planning to replace them yourself. A local garage door company will charge $75 to $100 labor plus the cost of a bag of rollers to install them.