The instructions on the are for Ubuntu 9.04 so i have tested them in 9.10. To enable the screen resolution button open a terminal and type the following:
sudo gedit /etc/acpi/events/asus-rotate-t91
then place these two lines in the file and save:
event=hotkey (ATKD|HOTK) 0000007b
Now reboot and your screen rotate button should work.