The rotation attribute. Technically it will be vertical. But you will have to turn your TV 90 degrees to read it.
I do not think there is a vertical scrolling behavior for labels because technically they are 1 line. The fact they can have multiple lines and span them is wrapping. The fact you can put chr(10) in there and simulate a new line is just simulating.
You could probably use animation to show your text as you move it behind a clippingRect but you would technically be bounce. Move slowly to top then to bottom then back to top (rinse and repeat forever) and do it all behind a clippingRect. That would be the only way to do it and you would have to write it yourself. It wouldn't be that hard to do.