Roller bearings use cylinders instead of spheres that means the contact between the inner and outer race is a line not a point (as shown in the figure below).

Thus, the load is spread over a larger area enabling the bearing to handle greater loads than ball bearings. Roller bearings are used in conveyer belt rollers where they hold heavy radial loads, however these bearings are not designed to handle much thrust loading.

Roller bearings are found in different varieties, such as spherical roller bearings, needle roller bearings, cylindrical roller bearing, thrust roller bearing, tapered roller bearing, etc.