public function roots() {
    return $this->node->newQuery()
      ->whereNull($this->node->getQualifiedParentColumnName())
      ->orderBy($this->node->getQualifiedLeftColumnName())
      ->orderBy($this->node->getQualifiedRightColumnName())
      ->orderBy($this->node->getQualifiedKeyName())
      ->get();
  }
public function roots() {
    return $this->node->newQuery()
      ->whereNull($this->node->getQualifiedParentColumnName())
      ->orderBy($this->node->getQualifiedLeftColumnName())
      ->orderBy($this->node->getQualifiedRightColumnName())
      ->orderBy($this->node->getQualifiedKeyName())
      ->get();
  }
Return all root nodes for the current database table appropiately sorted.

@return Illuminate\Database\Eloquent\Collection