src/Baum/Node.php
public function getRoot() {
    if ( $this->exists ) {
      return $this->ancestorsAndSelf()->whereNull($this->getParentColumnName())->first();
    } else {
      $parentId = $this->getParentId();

      if ( !is_null($parentId) && $currentParent = static::find($parentId) ) {
        return $currentParent->getRoot();
      } else {
        return $this;
      }
    }
  }
public function getRoot() {
    if ( $this->exists ) {
      return $this->ancestorsAndSelf()->whereNull($this->getParentColumnName())->first();
    } else {
      $parentId = $this->getParentId();

      if ( !is_null($parentId) && $currentParent = static::find($parentId) ) {
        return $currentParent->getRoot();
      } else {
        return $this;
      }
    }
  }
Returns the root node starting at the current node.

@return NestedSet