I have never seen a service manual for a Rover mower. There is an Illustrated Parts List for that mower (Model 18188 Autodrive) in the manuals area - we often use those to see how various parts of machines go together. For most ride-on mowers the user manual tells you how to make service adjustments. We don't have a user manual for an 18188, but there is one for a 53179 Autodrive in the manuals area.
Beyond that, I don't think there is any solution beyond contacting Rover's service department, or doing an internet search. Sometimes you can find out what American mower that Rover model actually is, and find the service information on the manufacturer's website. (Rover did not make ride-on mowers - it rebadged imported ones.)
