Roller bearings don't get hot boxes; solid bearings do.  Roller bearings can fail, but I believe that happened much less frequently than hot boxes with solid bearings. 

Maintenance is easier because all you have to do to change out a roller bearing wheel set and its bearings is jack up or lift the truck frame.  The bearings and wheel set can be dropped out. 

Changing a brass in a solid bearing is rather more complex, since you have to jack up the truck frame, then maneuver the old brass (bearing) out, possibly install a new gasket at the back of the journal box, maneuver the new bearing into place, lower the truck frame, and then pack and lubricate the journal box.

Todd Sullivan