Users without organisation admin permissions cannot see roles when setting Environment/Project permissions

### How are you running Flagsmith

- [ ] Self Hosted with Docker
- [ ] Self Hosted with Kubernetes
- [x] SaaS at flagsmith.com
- [ ] Some other way (add details in description below)

### Describe the bug

As an Environment / Project admin I can set permissions for users and groups for that entity. Currently they cannot do this for roles since the list of roles is not coming back for those users.


### Steps To Reproduce

- Login as a user that is an environment admin
- Attempt to edit permissions for a role in said environment

### Expected behavior

Non-org admins can retrieve roles but not edit them

### Screenshots

_No response_