I want to rotate the house. When I rotate on the Z axis, only house frame moves as one object. Other house assembly remains (actually rotates on different origin? How to remedy?
Unable to load your Blend file (still operating on Vers 2.77a) and probably not seeing what your helpers are referring to.
Going on your pic and on the face of it, the problem you appear to be encountering, might well be solvable by simply parenting all components to the one common parent and moving/rotating that instead.
I see 'parenting' has been mentioned in the comments/answers but would this make it a little clearer? ...
By making every separate component a child of a common parent, using the parenting feature, (CTL-P) not the child-of constraint, that parent (the Circle-Empty) should "localise" and hold all the bits & pieces together, with respect to the Empty. (and the house)
It's the empty you move/rotate around the scene, not the house or it's components.
The house and components would be forced to move with the Parent-Empty and importantly, their relative positions are maintained with respect to the house.
Individual components can still be moved around, scaled etc without affecting the 'bond'.
I apologise if I'm barking up the wrong tree here, I cannot see the Blend file, but if it helps... If not, say so and I'll delete this.
Select all of the objects by pressing 'A', then rotate by pressing 'R' + 'Z' to rotate on the Z axis. If you want to reset the origin of the other house to the same as the first part you have rotated, then set the cursor to that part of the house, then select the other part you want to reset the origin on. Go to Objec > Transform > Origin to 3D Cursor. Now it will rotate on the same origin.