Roller (G1)

Roller is a Autobot scout car in Generation 1 continuity.

Roller's one tough little autobot

It's is Optimus Prime's most unique but least commented upon feature that his body is composed of two autonomous units.

Optimus Prime's auxiliary "Prime" module, also known as Roller, is a small cart-shaped device that he uses to unobtrusively slip behind enemy lines. He can maintain radio control over it at distances up to 1200 miles. Having Roller present somewhere is like being there himself. Roller "speaks" in a series of electronic beeps and whistles.

Roller exploits a tactical opening

Although Optimus Prime can function as three independent modules, injury to any one of the modules is felt by the other two. Roller is particularly vulnerable, especially in the behind-the-lines situations in which he specializes.

Roller's is apparently "one tough little autobot", and he gets a cool upgrade in Battlestars.

Roller's battlestars toy features moterized tank treads, he becomes a convier belt in Star convoy's base mode

From Teletraan I: The Transformers Wiki, a Wikia wiki.