roller mill

Short definition from Wiktionary

Noun

1. 1
   A simple mill, often powered by animals, which grinds a material (grain, olives, chalk, etc) between a stationary horizontal stone disk and two vertical stone cylinders, in order to produce flour, olive oil, etc.
2. 2
   An industrial mill, usually electric- or steam-powered, which mills a material (grain, pigment, etc) between a series of rollers (often ribbed and usually operating at different speeds), to produce flour, etc.