It's not possible to delete a Role, the delete button is always greyed out in Roles page.

Steps to reproduce:
1. Login as admin
2. Go to Admin -> Roles
3. Create a new Role: "TestRole"
4. Go back to the page listing all Roles
5. Select "TestRole" and try to delete it

Expected:
Role can be deleted (it's an empty Role, so we should be able to do that)

Actual:
Delete button is greyed out