I don't know if the best solution is a height requirement. There are roofs like this where a stair got added just for that reason, that you can reach that roofs. Either you remove such stairs or change the roof turfing requirements.
Honestly Roof turfing wasn't that big of a deal. Not to the point where a whole script needed to be added. Especially when it totally alters the game play. It would be great if a script was added that only applied the height requirement on buildings that aren't accessible from the ground.
That would be to much effort and as far as I know Arran wouldn't add that. You would have to specific every area one by one.
Like people that monopolize the only one access to roofs and basically do the same thing as spawn killing while people try to reach them?