I have created my own file instead of mojoProfile.config and added a line to user.config to replace it.
In my file I have 2 profile properties, one with 'onlyAvailableForRoles="Managers"', the other with 'onlyAvailableForRoles="Customers"' (both "Customers" and "Managers" are existing site roles).
1. User in the role "Admins" has both properties.
2. It seems that (on pages /Admin/ManageUsers.aspx, /ProfileView.aspx, etc) properties visibility is based on current logged in user roles, but not on the roles of the user whos profile is being veiwed/edited. That is not correct.