In the year 874 B.K. (Before Khan), the system created the roles by understanding the needs mankind had. Before that, anyone who ventured inside the MAZE was given the title of explorer.
The system required extensive research and data gathering to create the Roles using events both inside the MAZE and outside of it to understand what was needed.
When the roles were finally created, all those above level 1 received a quest to perform a role change. Those who refused said quest received the roles of an explorer, and with time discovered the ability to use skills from other roles, albeit in a weaker state.
If you wish to learn more about each role, you can do so by heading to the pages below.