Couldn't know which drum roller was the problem, so bought four new ones (plus a new belt for good measure). Followed You Tube instructions and had no problems to speak of - carefully replace screws in reverse order putting parts back together. Cleaned lint from inside tubes and cabinet as part of the job. Biggest problem was disconnecting door switch from electrical harness.
Only one drum roller was bad (left front - closest to lint filter/exhaust from drum), but now have four new ones; plus, three spares if one of them fails.