A door assembly has a door header mounted on a frame defining a doorway, a door movably supported on the frame, and a track including at least one supporting surface along at least one side of the track. The track is secured to the door header. The assembly has at least one roller that is adapted to roll along the track. The roller has a rim portion adjacent a hub portion, and a tire material surrounding the rim portion that contacts the track. The roller is at least partially covered with a thermal barrier between the tire material and at least one of the rim portion and the hub portion to prevent heat transfer to the tire material.