If this was done in TG2, you simply need to figure how many degrees out it is, and add or subtract that number to the respective camera axis for each frame. It can be a bit strange to figure out, but if you do it on paper, its relatively straight forward. If you have to ajust more than one axis though, it can be quite daunting.
ALLLTERNATIVELY... one could look for or create a utility that renders the cubemap and simply rotates and snaps new images for each side. It's a seamless skybox, so there is no reason why you would need to re-render anything.