Oatfield sits in a cold-moderate climate band, which matters more for rollers than people expect. Steel rollers without a bearing seize up stiff in a cold snap if the old grease has gone gummy, and that stiffness is what cracks a brittle hinge or bends a stem that's already thin from corrosion. Nylon rollers don't have that problem, which is part of why we recommend them for a door that sits in an unheated garage through the winter.
The other complication is the track itself. A roller job on a straight, true track is quick. A roller job on a track that's been reshaped by five decades of use, minor impacts, and prior owners' repairs takes longer, because truing it properly means checking every bracket, not just the two closest to the bad roller.
We'll tell you straight if what looks like a roller problem is actually a door that's reached the end of its working life - on a door this old, sometimes replacing the whole section costs less over five years than chasing one worn part after another.