[ovirt-users] Some roles management issues

Hi list, access policy to my system has changed recently and now I've to manage non admin users allowed to create VMs only on selected resources. Unfortunately this condition was not expected years ago when the system was installed and so all VNic profiles was created with the option "Allow all users to use this Profile", there is a way to edit this settings after a VNic profile was created or I need to create a new one and set all VMs to use that? The same procedure is applicable also for the network used by the hosted engine? I've tried to remove the "VNicProfileUser" role assigned to "Everyone" for a particular VNic profile but by doing only this users continue to see the logical network in the select box of the VM creation form but they cannot use it getting an error when they effectively create a VM clicking OK (that is quite annoying because it seems a configuration problem). I've also noted that the role "DiskProfileUser" was assigned on storage domain object and to some unknown null object for "Everyone", there is some reason why some roles are assigned to null? I could safely remove them? Greetings,     Paolo