A pump having a rotary portion which compels the movement of a fluid by peristaltic compression of resilient tubing containing the fluid includes a roller assembly having at least one roller mounted in the rotary portion of the pump for contact with the resilient tubing. The roller has a range of rotation in contact with the tubing during pump operation. A roller control mechanism is adapted and constructed to stop the roller at a single, predetermined location on the tubing when the pump operation is stopped.