If a model is out of range it doesn't roll to hit so can't overheat. They must know they are out of range.
Plasma Guns overheat a silly amount already. No, you don't need to roll since you never actual fire the gun. The Bolters find range for the Plasma if you need a fluff explanation.
I usually lose 3 Plasma Cannon troopers to self-inflicted wounds in a given game anyway, so there's no point making things even more ridiculous.
Let me try to break it down for you.
Sorry to be rude, but have you payed attention to the last couple of posts. The rules state if it is out of range, it *automatically misses*. this implies that shots have been fired and therefore the weapon can overheat even if not in range
The Helblaster has its own very different set of special rules. It's a completely different weapon, in a completely different game.I think yes you do have to roll to see if it over heats because a similar thing happened to me with my helblaster volley guns in my Empire army.