We need the ability to define roles and assign authorization permissions to these roles.
We need to be able to assign roles to groups and/or individuals.

You can create/read/update/delete roles with the VG WinConsole and/or the VG WebConsole, or creating your own role management system using VG API.
In the VG WinConsole and the VG WebConsole, you have the possibility to grant permission sets to roles.
You also have the possibility to grant a role to a user or to a group.
If you grant a role to a group, all the users and groups inside this group will have the permissions related to this role.