Well then i'd suggest adding the rule: "do not destroy friendly ladders"
You say roof campers cause you grief, but come on. Grief? That's ridiculous. You are just pissed off that archers get to have a safe spot on most maps.
The problem here is not the roofs or the roof camping, it's the fact that those roofs are often unreachable because nobody on your team (including you) have the sense to bring a ladder to a village fight.
Im all for archers having some kind of protection from infantry & cavalry, but roof-camping houses that are not supposed to be camped in the first place, is not it. Take the native maps, most of them have places where range can stand and shoot at other players with some protection. IE high-ground, staircases, roofs with built-in-ladders. These are fine.
Whats not fine, is facing roof-campers with no possible retaliation against them, until everyone else on their team is dead.
Its not fine that infantry & cavalry have to kill off the entire enemy team, save for those campers, before they are able to touch them.
In my eyes this is grieving, its a loophole in the rules, that allows them to stay alive until the end of the match, while being able to rain down arrows on their enemy.
About ladders, its not always a viable tactic to bring a counter-ladder.. Reason being, on some maps you have to walk 1-2min just to get to their camping spot. Chances are, you wont be making the run alive, ladders seems to attract extra attention (arrows & lances). Also its easier to camp the other side, but do we really need more lame tactics?
Two wrongs don't make a right.