... therefore due to the large temperature variations (and therefore thermal expansion) within a shaft of a turbine engine, typically one bearing is a ball bearing which takes radial loads and also locates the shaft axially in both directions, absorbing the thrust loads, whilst the other(s) is a (are) roller bearing, taking the radial loads but allowing for movement of the shaft due to thermal expansion.
I don't think that taper roller bearings are used much - they can absorb radial and axial loads but they can only absorb the radial loads if there is lots of axial load - might be OK whilst the engine is producing lots of power but no good on shutdown etc.
I think that is an expanded version of what minigundiplomat was saying!
HC