This chapter deals with the designs and operation of different types of roll crushers. Two main types are indicated. The first type where the rolls are rotated in opposite direction with one roll spring loaded. Here, the mineral particles are nipped and crushed as they pass between rolls. In the second type, known as high pressure grinding roll (HPGR), the mineral sizes are reduced by compressive and interparticle pressure. The forces responsible for communication in each case are illustrated and the mathematical laws involved are explained, using solved examples. Commercial circuit diagrams of integrated plants are illustrated to help understand the theory and their practical applications.