Roles are commonly used to give certain tasks for players to fill out in large groups or Tribes/Camps.
Use and Execution
Roles are given to people in a large tribe or group to perform a certain job 24/7 to output maximum activity among the group. For example, the leader of the tribe would send about two people to go mining for ores. They'd send some to bake food, and some to protect certain areas while the leader does all three. Sometimes it is taken into more serious handling, and may even be chopped down to help desk officers or merchants if there is usually a large village present.
It is unwise to assign roles early on in a tribe. At least 5 people should be present so you are prepared for overall attacks, and at least 2 should be assigned to keeping peace and harming either trespassers or thieves. This keeps order among the group and allows people to continue to gather and cook, along with building.