Roller assembly for ground-engaging track system

A roller assembly for a ground-engaging track system includes a roller forming a shaft bore, and a roller shaft within the shaft bore and having a circumferential ramp surface. A roller retention system for the roller assembly includes a roller retention collar with an outer peripheral surface, and an inner peripheral surface that may include a wedge surface structured to friction fit the retention collar, within a collar bore in the roller, upon the circumferential ramp surface to limit axial displacement of the roller upon the roller shaft. The roller assembly may include two roller retention collars supporting the roller against axial displacement without use of thrust washers or the like, and fixing the roller and roller shaft to rotate together relative to a track roller frame.