"The Role Manager feature has not been enabled." in web.config

Question

I have an MVC4 application with the models and the migrations in a separate project, which is a class library.

I have this in my seed method:

protected override void Seed(BDOleoTorres.Models.OleoTorresContext context)
    {
                if (!Roles.RoleExists("Admin"))
            Roles.CreateRole("Admin");
            //[Authorize(Roles = "Admin,Vendedor,Administrativo")]
            if (!WebSecurity.UserExists("Administrador"))
            WebSecurity.CreateUserAndAccount(
                "Administrador",
                "Admin123.",
                new { NrVendedor = 1, DataHoraCriacao = DateTime.Now, NomeHumano = "Sr Administrador", TipoUser="Geral" });

        if (!Roles.GetRolesForUser("Administrador").Contains("Admin"))
            Roles.AddUsersToRole(new string[] { "Administrador" }, "Admin");

    }

And this in my web.config (other project):

<system.web>
<roleManager enabled="true" defaultProvider="SimpleRoleProvider">
  <providers>
    <clear />
    <add name="SimpleRoleProvider" type="WebMatrix.WebData.SimpleRoleProvider, WebMatrix.WebData" />
  </providers>
</roleManager>
<membership defaultProvider="SimpleMembershipProvider">
  <providers>
    <clear />
    <add name="SimpleMembershipProvider" type="WebMatrix.WebData.SimpleMembershipProvider, WebMatrix.WebData" />
  </providers>
</membership>

I do correctly migration, but when do update-database -verbose have the error:

The Role Manager feature has not been enabled.