two heavy sliding doors with mirrors used for closet failed to slide on track. removed doors and then roller assemblies. cleaned with metal brushes, WD40 and lubricating oils to unstick ball bearings. successful with 3 out of 4 and restoring ability of rollers to spin freely. reinstalled two assemblies into one door which now can slide in track. 4th still stuck even after long soak in WD40 type oil and considering replacement. width of assembly is 5/8", height 2" and concave roller wheel is 1 1/8" diameter. Looked at your site and see three possible candidates part numbers
81-250,
81-251 and
81-083