Autocast Roar

So, as a disclaimer, I've never really had to ever delve into the ability editor, since the only map I've ever really finished was a risk map. I've been wondering how to do this, but couldn't find a solution.
Doesn't appear to be a field in the editor to make an ability autocast or not. I thought about adding an item bonus to units in a range after the autocast roar ability is cast, but that doesn't give them a % bonus and I if I understand correctly, autocast abilities aren't detected by normal means.

You can use the event "A unit is attacked." Then, for condition, check against unit type. If it's the right unit type, order the "Attacking Unit to "Night Elf - Battle Roar." Or whatever the thing is... It should work... And should be fine. This will order them to use the order even if it's on cooldown and such, but it's better than adding every unit to "A [unit] is damaged" event... I suppose. Alternatively, you may also use "A unit is issued an order targeting a unit"... Then check for "Ordered Unit" == Some unit type and issue the battle roar Order ID... Anyway, this is the easiest solution, as long as you don't mind the issue of this trigger firing when it "shouldn't"...

You can use orb of lightning (new). If the ability is turn on, check it with triggers then add Orb of lightning (new) to your character with its proc ability to Roar. Then you can hide that with spellbook trick.