Abstract: An improved combing or opening roll assembly for open-end spinning machines includes means for cleaning the inner cavities by direct axial injection of compressed air into the cavity, and an outer surface configuration designed to inhibit or prevent accumulation of microdust and fibers thereon. One outer surface of the roller unit includes a color-coded speed indicating means which enables an operator immediately to visualize the relative speed of rotation, as a safety factor decreasing the likelihood that an operator would inadvertently touch the combing ring during rotation.