Disc Hubs and Rotor types.

Rohloff uses a 4 bolt disc: http://www.rohloff.de/en/products/sp...scs/index.html

6 bolt rotors can be used on centrelock hubs with an adapter but centrelock rotors can't be used on 6 bolt hubs.

Shimano-Centerlock-To-6-Bolt-Adapter

Probably also worth mentioning that there are two types of mechanical disc brake calipers, Road specific and Mountain specific. The two types have different pull ratios for use with certain levers.

Road versions work with drop bar levers and cantilever type levers.
Mountain versions work with v-brake levers or linear brake levers.