My map is arena style, and when there is a victor I need it so the host can select an option to restart the game from beginning or have it automatically restart.
Show a dialog to the host with 2 buttons on it : restart or don't restart.
In a trigger, detect when a button for your dialog is pressed. If that button is equal to the Restart button, then restart.
The rest would depend mostly on how your map is made. You'd have to remove all the hero, summoned and such units from the map and give them a new wisp (or whatever unit) to select their hero. Don't forget to re-set their resources.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.