A device (20) for root-rolling a thread (T) on an object (O) includes: a body (21), an accumulator piston (24) mounted for sealed sliding movement within a body passageway (22), a coarse adjustment screw (25) threaded onto the body, a Belleville spring stack (26) compressed between the coarse adjustment screw and the accumulator piston, an actuator piston (28A or 28B) mounted for sealed sliding movement within a cylindrical opening (23) in the body, and a thread roll (32) rotatably mounted on the actuator piston. A fine adjustment screw is threaded (33) into a first opening (34) on the body, and communicates with a fluid chamber between the accumulator and actuator pistons. The positions of the coarse and fine adjustment screws may be selectively adjusted to controllably vary the fluid pressure within the chamber. The device may be mounted on a machine tool (35) and selectively moved toward the object to root-roll a thread on the object when the object and device are rotated relative to one another.