Rotating on anything but the vertical axis requires mods.
Additionally, free-rotation on the vertical axis also requires mods.
Scaling components also requires mods.

There are a couple of arch-like components that are unlocked later (such as the arched double doorway), perhaps that's what you've seen?

I hope the devs allow rotation on more axes (and possible scaling) , as it'd allow for drastically more sophisticated constructions without needing to unnecessarily inflate the construction palette.
In fact additional rotation & scaling controls would allow the construction palette to be shrunk, as a significant portion of the existing components would become redundant.