Symfony 2.6 checked by default checkboxes

How I can make checkboxes checked by default based on data from database?

Now my form looks like:

      ...
      ->add(
        "role", "entity", [
          "class"    => "AppDefaultBundle:OptionRole",
          "required" => false,
          "label"    => "Roles for user: ",
          "property" => "name",
          "expanded" => true,
          "multiple" => true
        ]
      )
      ...

And I want to select defaults for this checkboxes based on data from other table.