With interfaces like rod bearing, the important thing is very tight tolerances to reduce play or slop in the joint. The more moving parts you have, the more slop is present. Where something simply spins and has no forces from the side, like in a transmission, roller bearings work well. But a crankshaft experiences high forces from the side.
Take a look at the crankshaft...any crankshaft. Notice how it is designed.
Only place a roller bearing could work would be the front of it.
And a bearing does not have to be a roller in desgin. Bearings are designed for one thing only, and that is to cut down friction. So long as the bearing material is softer than the metal it is protecting. Often times cam, main, and rod bearings are known as "sacrificial" bearings because they WILL wear out before the assemblies do.