BillAcito has it right. While some of the die and BGA creation tools, like the BGA/Die text in wizards, allow you to specify the rotation when the component is created, that is not available in all flows. What is available is, after placement, the ability to rotate, move, and mirror the component. You can do this using:
Edit -> Move (allows for rotation as well as movement; available for both APD and SiP users)
Edit -> Spin (allows for rotation only; available for both APD and SiP users).
Edit -> Diestacks... (allows for rotation, movement, and pad layer change; available only for SiP users).
I believe stacked die packages are only supported in the SiP products, so with luck that is what you are using. If so, the die stack editor tool is the most comprehensive, as it also gives you options for what to do with the bond shell if it exists (stretch the wires to the new pin locations vs. move the wires, fingers, and die as a single unit) and the ability to change the ordering of the dies in the stack by changing the layer that each die is placed on.