Problem Description: Users with group permissions can visit `/ui/roles` and /ui/roles/create` which results in permission error.

Reproduce:
1. create user `testuser`
2. create group `testgroup`
3. add `testuser` to `testgroup`
4. assign the existing role `galaxy.group_admin` to `testgroup` (or create a role with group permission `View group` and assign it to `testgroup`)
5. login as `testuser`
6. visit `/ui/roles` or `/ui/roles/create`

Proposed Solution: Users shouldn't be able to visit `/ui/roles` and /ui/roles/create`, only the superuser and admin should be able to do this. The user should be redirected to the `You do not have permission to perform this action` screen. Menu item `Roles`  in the sidebar should be hidden as well.