You can set up a raid pool with a specific Raid Roster on the Admin Menu -> Features -> Rapid Raid -> Pools area of your site.
Role Based Signups
You can add players to Groups and Roles on this page, then you can use those groups as the Auto-Fill setting on signup groups for the raid.
Determines Who is Raid Active
If you have set this pool to only consider characters on the Raid Roster as ‘Active’ then players in at least one Role in the area above are considered ‘Raid Active’. Raid Active players show on the Members list by default. You can create a Raid Roster with as simple as a single group called ‘Raiders’ with a single role of ‘Active’ or make much more complex groupings.
Organizes Your Raiders
Some guilds just want to communicate what roles people fill in raids. The raid roster is perfect for this.