How to throw your opponent over the top rope in a Retro Rumble
When you have an opponent in a headlock and are near the ropes perform a body slam by pressing weak + Up. You should be facing the center of the ring when you do it. Note that your opponent should have less than half their health in order for this to work. It can be done if they have more health but it is rare.
While your opponent is prone in the corner and if they are low on health use a wrestler with a strong move that is a dropkick or the wind-up punch or perform a 3 punch combination by pressing the weak button 3 times in a row. This will send him over the top rope.
RetroMania Wrestling – Finishing Moves & Finishers