To reproduce:
1. Create 3 new roles "Admin A", "Admin B" and "No-Admin".
2. Assign these roles to different permissions but "admin project" only to "Admin A" and "Admin B"
3. Let a real Jira-Admin assign a non-admin user to role "Admin A".
4. Login as non-admin user and got to role page.
5. Add yourself to role "Admin B" and "No-Admin".
6. Now make this undone and try to remove yourself from role "Admin B" and "No-Admin"

Removing from "Admin B" will fail with

You can not remove a user/group that will result in completely removing yourself from this role.

This should be possible, but Jira does not remember from which role the user started his action.