Andrea,
the command works, but that will be harder than just ask a rotation.
First forget the landscape / portrait.
Second, you will need to change your approach of smartforms. It's not just a command to say rotate everything, it's a command to say rotate the text. So you will have to define windows starting to the upper left corner has they didn't have rotation. And you will have to write the text with rotation.
Start with something simple, you will understand : A window with border, a simple text like SY-ABCDE.
May the force be with you ! 
Fred