Another important advantage to roller bearings is the markedly reduced initial resistance, meaning that roller bearings start rolling with much less effort than solid bearings. Up here in North Dakota, temperatures often go below zero, sometimes to -20 to -30, and can stay below zero for weeks at a time. In winter, tonnage ratings for steam locomotives dropped considerably because of the higher resistance due to cold bearings, in large part because the oil/grease would solidify in the cold. I don't envy the steam era railroaders having to work through a North Dakota winter. There were all sorts of operational challenges they had to contend with which are now largely mitigated by technological advancements.
And yes, weeks of below zero weather is as awesome as it sounds. Ask me how I know.
