A gyroscopic roll stabilizer includes an enclosure, a flywheel assembly, a bearing, a motor, and a bearing cooling circuit. The enclosure is mounted to a gimbal for rotation about a gimbal axis and configured to maintain a below-ambient pressure. The flywheel assembly includes a flywheel and flywheel shaft. The bearing rotatably mounts the flywheel assembly inside the enclosure for rotation about a flywheel axis. The bearing has an inner race and an outer race. The inner race is affixed to the flywheel shaft, and the outer race is held rotationally fixed relative to the enclosure. The motor is operative to rotate the flywheel assembly. The bearing cooling circuit is configured to transfer heat away from the bearing by recirculating cooling fluid along a closed fluid pathway. The gyroscopic roll stabilizer is configured to transfer heat away from the inner and/or outer race of the bearing to the cooling fluid.