In general, we do not recommned the use of roatation as it is NOT a hardware feature. We implement it is software in the driver by creating a fake frame buffer to the OS that is in the rotated resolution, then for every frame, we re-render the data to another framebuffer that matches the actual physical display resolution and then shift that data out to the display. It has a very limited acceptable use case for rotation and negatively impacts driver performance, and has limited capabilities. It is best to find a actual display that matches the needed orientation, or use the display in its proper designed unrotated orientation. The limitations to rotation are documented in the USers Guide and in White Papers available for the driver.
Hope this helps.