It looks like it should be but probably isn’t. Examining my machine, the shaft on the roller looks to be about 3/4" long. I don’t know, maybe the gantry could be unmounted and skewed enough to reach it, but it might require removal of both sides of the top, disconnecting the power, and coolant from the tube so the gantry can be removed for access that roller. Understand, the machine has to be assembled, it can be disassembled. Depends on your resolve and mechanical ability.
Personally, faced with an unknown like that, I figure if it was done by Humans, I belong to that club. If I don’t know how to do it - I will by the time I’m finished.
The problem with that approach is the first lesson learned is usually how not to do it.
At one time I could I could changed the oil in the car, install a water heater and weld a pipe to the water heater —to have a water shut off valve in the house. In January, I had to replace the two front Glowforge carriage wheels.
I learned a few things last night.
The gantry still moves smoothly without the broken piece.
This makes me think the GF could still run smoothly without that broken piece. I know that will probably cause pressure for the right acrylic wheel cover.
The naked wheel does not touch the rail as it is being moved.
The part at the top of the green arrow has the ability to be pushed down. There is give when trying to push it down because it is attached to a very tiny little bar that has a spring. The bottom green arrow is the location of the tiny little metal bar.
The spring loaded bottom wheel clamps that side of the gantry to the rail, without it that side is just sitting there. I would expect accuracy and alignment issues without that wheel in place.