=.= thats not the standard gui texture to what I am referring to, thats a gui box with a texture in it, thus when I said that other means may be possible was true, but "GUI texture" from the GameObject -> Create Other -> GUI texture menu can not be rotated.
using this standard method, rotate object, rotate gui or any other rotate, even manually entering it in the objects location in the inspector view will not rotate the standard GUI.
As such I do belive that the method you are using is the code version of unities UI that playmaker exposed for our use, this if I am correct is the onGUI () or something like that function within unity script.
to the opening post, I have not used this part of the UI, I had only started with the default gui text and gui texture and moved onto ngui.
I can confirm that the below, using playmaker and gui box and rotate gui does work, im not sure how to use the playmaker script part of gui or its limitations (if any) let us know how you get on with it.