Membuat HakAkses Laravel dengan 2 table

Saya membuat HakAkses user , Admin dengan laravel dengan 2 table yang berbeda .. scriptnya

    public function up()
    {
        Schema::create('Users', function (Blueprint $table) {
            $table->increments('id');
            $table->unsignedInteger('roles_id')->nullable();
            $table->string('username')->unique();
            $table->string('name');
            $table->string('email')->unique();
            $table->string('password');
            $table->rememberToken();
            $table->timestamps();
        });

        Schema::create('rules', function (Blueprint $kolom){
            $kolom->increments('id');
            $kolom->string('nameRule');
        });

        Schema::table('Users', function(Blueprint $kolom){
            $kolom->foreign('roles_id')->references('id')->on('users')->onDelete('cascade')->onUpdate('cascade');
        });

    }

class RegisterController extends Controller
{
    public function GetRegister()
    {
    	return view('Register.FormRegister');
    }

    public function PostRegister()
    {
        $user = new User();
        $user->username = Input::get('username');
        $user->name = Input::get('name');
        $user->email = Input::get('email');
        $user->password = bcrypt(Input::get('password'));
        $user->roles_id  = DB::table('rules')->select('id')->where('nameRule','user')->first();

        // dd($user);
        $user->save();
    }
}

    public function user()
    {
    	return $this->hasMany(User::class);
    }

class User extends Authenticatable
{

    public function role()
    {
        return $this->belongsTo(role::class);
    }

*sesudah table rules diisi 2 coloum yaitu - id = 1 & nameRule = user - id = 2 & nameRule = admin

*bila tidak diisi table rules error tidak muncul

*mendapatkan Error

#ErrorException in helpers.php line 747: #Object of class stdClass could not be converted to string