Rollers that use the plate attachment where the end plate is flush with the end of the culvert plastic were a little difficult to figure out how to reattach the plate. If a bolt comes loose the nut is probably rattling around inside the roller. You'll have to remove the end plate, replace the bolt, tighten everything down securely, use Locktite to keep the nut from loosening again, then reinstall the end plate.
First the bearing lock collar has to be loosened and pulled away from the bearing
Next the shaft has to be pulled out of the bearing and back flush with the frame
Next the three 3/8 cap screws, 9/16 head/ need to be removed from the plate.
The plate should now be free to be pulled out of the culvert.
The latest model roller uses a 3/8" hitch pin to lock the axle in place.
The bearing is held onto the shaft using an eccentric lock collar. The lock collar is held in place by a small allen screw that can be seen on the upper part of the lock collar. The roller axle can develop rust between the bearing and the shaft. Spray WD40 or other rust loosening spray and let it soak for a few minutes before attempting to pound the axle out of the bearing.