The present invention provides an adjustable roller assembly for doors which slide on tracks. The adjustment mechanism can be used to take up slack after the door is installed on a track. Numerous arrangements of this general type are shown in U.S. Pat. Nos. 2,990,567, 3,237,238, 3,716,890, 4,134,178, 4,189,870 and 4,353,186. None of these patents discloses the features of the present invention.