Roll control is provided for a device by controlling the roll-angle offset about the device roll axis in correspondence to a specified rotation of a reference frame for the device. This specified rotation may correspond to a roll-free rotation of the reference frame to align a corresponding reference roll axis with the device roll axis. In applications to robotics generally, the device may be characterized as a robotic element or a robotically-supported instrument. In specific applications to robotic surgery in a computer-assisted medical system, the device may include a spar or cannula that is configured to support a surgical instrument.
