Why are Roller Bearings used in the hot section (Turbine Drum) of a Jet Engine?

Unlike Ball Bearings, the Roller Bearings allow some axial movement. When a turbine engine is operating the temperature of the hot section is very high, which result in linear expansion of the shaft in the hot section. To allow this linear expansion we use roller bearings in the hot section. If this was not the case, and we would have used the ball bearings which do not allow axial movement of the shaft, the linear expansion due to heat could deteriorate the engine.

To see the difference between Thrust and Radial loads, follow this useful link: How Stuff Works

P.S. Correct me where I am wrong