A roll control actuator for a stabilizer bar includes an outer housing that is fixed to a first bar portion and a shaft that is fixed to a second bar portion. The shaft is helically connected to a piston that is received within an interior chamber formed inside the outer housing. The piston separates the interior chamber into first and second fluid chambers. An anti-rotation mechanism is fixed to the outer housing and cooperates with the piston to restrict the piston to axial movement relative to the outer housing. The first and second fluid chambers are selectively pressurized to control roll stiffness by moving the piston within the outer housing.