[Gumby]

Roller bearings are not a new thing... as others have stated durability, complexity, and cost are all good reasons why not to use them in the crankshaft. Why complicate the equation when plain hydrostatic bearings do just fine?

A good example is the spindle head of a milling machine. I can't think of a single industrial (CAT40 or larger) mill that has roller bearings in the spindle. Most of the high end machines used in high speed machining use either air bearings or plain fluid bearings and some even use high powered magnetic bearings. If you want to spin something at 10k - 20k rpm or more under load you simple don’t use roller bearings, there are much better options.

Besides a slight reduce in startup friction what would you be trying to gain out of using roller bearings?