While ranks usually determine the appointment of a certain officer in real armies, in reenactment we need to rely on smaller groups of people to fill a large variety of positions in order to represent all aspects of Roman military life. Consequently, there is less restriction about which rank an officer must hold in order to fill a certain appointment. 

We are a Praetorian Cohort within Nova Roma Australia, we follow the rank structure set out by it.

Given the reality of lesser numbers in a small group members can take on more than one role where such role does not provide a conflict of interest. Likewise multiple members can be of same rank but only one member can be assigned to certain tasks within the organisation.