A little late for that, isnt it?

On the other hand, they could easily move them elsewhere ...
Wich would have same effect, with MUCH less needed effort.

Oh but Ogres do have ranged attack, as 1varangian mentioned, they are throwing stuff ... were throwing boulders in the past, but if you run behind edge of that roof ... they have no line of sight to attack. :-/
I admit that i didnt try that, but i belive that Stealth was not even necesary in this case ... therefore making it Action (even tho it would help in other situations) would solve nothing here.

I mean smart AI would most likely run out of your AoE ... and then even futher, out of your ranged attacks ...
Then the game would either stuck in stalemate situation ... they would refuse to come closer, you would have no way to attack them ... so you would send one of your characters down as a bait ... they would rush to attack, but that would most likely take more than one turn, so you would attack them with Ranged attacks ... and simply climb back to the roof once they would get too close ... so they would start running away again > another round of ranged damage.
>> The result would be basicaly the same, cheesed fight with little to none effort from player.