How to make a force dependent on the angular velocity

I am simulating a kind of roller in Solidworks Motion Analysis and I want to know how much time the roller will need to achieve certain speed. It is driven by a motor with a specific torque/speed curve. Adding a constant torque is not an option because it should decrease with the increase of the angular velocity. Is there a way to make the amount of torque dependent on the current speed of the roller, thus satisfying the motor characteristics?