Is there really no way to rotate buildings?

[Deathmort]

at all?

[Gambit_DoW]

Yes, of course brother. There is an ORIENTATION field, in the STRUCTURE_EXT of each building entity.
For example, have a look at
Data\attrib\ebps\races\space_marines\structures\space_marine_hq.rgd
The orientation there is 0. Try to set it to 90 or 180, and you will get it shifted.
BUT this is a bit tricky, as it will not rotate the building's initial dimensions.
So for non-squared buildings, you must also look into entity_blueprint_ext.
For a 90 or 270 degrees rotation,m you must swap the scale_x and scale_z values (the _y is the height, so no change there).

It is a bit technical, and needs modding knowledge.
... And it is NOT perfect.
But it can be done :)

[K84]

You can mod buildings to have different orientations, like Gambit said, but there's no way of actually rotating buildings whilst in-game.