Pick the object up first
Pick up the item so it follows the cursor and is ready to place. In the English Windows keyboard-and-mouse controls described by the checked sources, Z and X rotate it in opposite directions. These are item controls, rather than camera rotation controls.
Dragging with the left mouse button can provide finer rotation; Left Ctrl is also used when adjusting the grid and snapping. Check the actual controls and snapping state in your game before relying on a particular combination.
Rooms, arches and keyboard layouts
Pick up a room as a whole to rotate the room. Editing an item inside it does not select the entire room. Wall arches have their own placement constraints, and their orientation follows the wall.
If rotation does nothing, confirm that you are moving the intended object and check your key bindings. A Dutch PC control reference uses W/X, so Z/X should not be treated as universal across keyboard layouts.
If Z and X do not respond
An older Windows report described Left Ctrl + Z/X working when Z/X alone did not; the developer response pointed to Use Room Item Snap. Treat this as a troubleshooting lead for that environment, rather than a required combination or a confirmed fix for every version.
Success means the object’s direction visibly changes and it can still be placed in a valid position. Console and Steam Deck bindings are outside this guide’s scope.