You can use the API - security-login-role-create
Possible access level settings are none, read-only, and all. The default setting is all.
Ruby code for this would look like:
 request = NaElement.new("security-login-role-create")
  request.child_add_string("role-name", new_resource.name)
  request.child_add_string("vserver", new_resource.vserver)
  request.child_add_string("command-directory-name", new_resource.command_directory)
  request.child_add_string("access-level", new_resource.access_level) if new_resource.access_level
  request.child_add_string("return-record", new_resource.return_record) if new_resource.return_record
  request.child_add_string("role-query", new_resource.role_query) if new_resource.role_query
  result = invoke_elem(request)