a rolling device such as a roller ski or in - line skate that uses a roller of a hard material with the roller mounted to the frame of the roller ski or in - line skate in such a manner that it can be forcibly moved to contact the elastomeric wheel of the roller ski or in - line skate , causing the softer elastomeric material of the wheel to displace about the harder roller , resulting in a significant increase in rolling resistance with minimum frictional wear . a roller ski or in - line skate that uses , in conjunction with the aforementioned roller , a lever actuated brake permitting the roller ski or in - line skate to be stopped on down hill slopes .