Heavy-duty slow-rotating roller chains are expensive and time-consuming to replace. Inspections to assess the wear on a chain can only be carried out periodically and usually lead to a standstill of production, which comes with a loss of earnings. Therefore, the incentive to maintain them only when needed, and to use them as long as possible is high. Thus, the use of condition monitoring for roller chains is justified. It can continuously determine the remaining wear margin of the chain so that maintenance can be scheduled when necessary and production holds can be minimized. For slow-rotating roller chains the usual frequency-based approaches are not applicable. We propose the average torque of the driving motor for the roll-in of each chain link as a meaningful condition indicator. The angle and torque can be read out from the motor drive and encoder, respectively, and the average torque can easily be calculated. On data from a highly worn chain of a demonstrator, the roll-in of certain chain links lead to a 25% increased average torque of the driving motor. We expect the average torque to gradually increase with less remaining wear margin.