You can make the building a unit, make it face in the editor (Ctrl + Click) and then make the unit a building again; any value you change in the building afterwards will make the Building face it's default degrees again. That only works for pre-placed buildings.
You can also do it with triggers during gametime using "Unit - Set unit facing"
I think there's a default building face degree in the gameplay constants, but that will apply to all buildings.
You can, alternatively, rotate the camera angle, instead of rotating stuff.