The ability to assign multiple roles is part of the premium plan and is not available on the Free or Basic plan.
When setting up an Organization on Track it Forward, the person creating the Organization Account is by default the Owner. Only the owner and managers are able to assign roles and permissions.
To do this, go to Organizer Dashboard
In the Volunteers menu tab, click on the specific volunteer you'd like to upgrade.
Click on the Permissions tab, and select the role that you'd like to upgrade them to. You are able to assign multiple roles to volunteers, but this has to be done one at a time. This is also where you can remove roles from people.
Once the role is assigned, the system will notify you on top of the screen.
To learn more about all of the roles and their permissions, read this article.
Any new volunteer that comes in either via an import, self-registering, or by invitation, are not given any special permissions.
To give them additional permissions, see the steps above.