swfdisplayitem->rotate() sets the object's z-order to depth. Depth defaults to the order in which instances are created (by add'ing a shape/text to a movie)- newer ones are on top of older ones. If two objects are given the same depth, only the later-defined one can be moved.
The object may be a swfshape(), a swfbutton(), a swftext() or a swfsprite() object. It must have been added using the swfmovie->add().