Slabs created with the Slab Tool do not rotate outside of the x-y plane by design.
Slabs created with the Roof Tool can be angled ... but not to 90 degrees...
If you want something slab like rotated 90 degrees from the x-y plane, that is the Wall Tool.
Maybe I'm not understanding what you are asking since these are basic new user things...?
If you are just creating a shape rather than a building element, you can rotate/edit Morphs any way you like, similar to SketchUp shapes. You can start with a slab or whatever and convert it to a Morph.