Building a prison in Prison Architect is one of the best parts of the game. Choosing where you want all the room objects to go can take you awhile, and luckily the game doesn’t restrict you in which direction items need to face. (Despite characters seemingly being able to hover over anything.)
To rotate objects in the game, either hit the middle mouse button or the R key. This will rotate your object clockwise. Note that not all objects have many different rotation positions.
Voila, you now know how to rotate objects in Prison Architect. Get to building the perfect prison!