Scene.GetRootGameObjects

public GameObject[] GetRootGameObjects ();

Returns

GameObject[] An array of game objects.

Returns all the root game objects in the Scene.

public void GetRootGameObjects (List<GameObject> rootGameObjects);

rootGameObjects

A list which is used to return the root game objects.

Returns all the root game objects in the Scene.

Please make sure the list capacity is bigger than Scene.rootCount, then Unity will not allocate memory internally.