Roller bearings are stumpers that work in the dark. The roller bearings that have learned more by doing so may be sheltered in a nice greasy warmth, but the asylum seekers among the bearings are having a hard time. They live in the outposts of technology.
For engines, these are steering and rear fork bearings. In cars, for example, these are the bearings of rear wheel bearing arms. The maintenance of those things is really in workshop manuals.
But why are they so often forgotten?