I'm not 100% sure but I thought Rover ceased production in 2005? Anyway, when the car is made has nothing to do with when it's registered. In effect you could manufacture a vehicle in 2008 and keep it stored for several years before registering and selling it. It is the date that the vehicle is registered that determines it's number plate. There are various ways of determining when the car was manufactured by tell tale date stamps on the vehicle parts. The number plate is the last thing to be added!!