A surgical assembly includes an electromechanical instrument and an instrument drive unit. The electromechanical instrument includes a housing portion and a shaft. The instrument drive unit includes an outer shell, an inner hub, a first motor, and a second motor. The outer shell is configured to be selectively coupled to a robotic arm. The inner hub is rotatably disposed within the outer shell and configured to be non-rotatably coupled to the housing portion of the electromechanical instrument. The second motor is disposed within the outer shell and includes an outer stator fixedly coupled to the outer shell, and an inner rotor rotatably disposed within the outer stator. The inner rotor has an inner surface that defines a longitudinal channel having the inner hub non-rotatably disposed therein. Actuation of the second motor rotates the inner hub to effect rotation of the electromechanical instrument along a longitudinal axis thereof.