Even if ladders are indestructable going up a roof with 8 ranged is still suicidal. A ladder does not allow you to dodge much, which means that roof is fully immune to anyone without a shield. Even with a shield they can often shoot your from multiple angles on many roofs making you unable to get up there safely, and that is assuming 180 degree shield protection, only the widest shields with high shield skill even provide that. Even then you got up a roof as a shielder, all the archers get out their instastab 1h swords, the few crossbowmen in there start their 8 athlethic blunt weapon dance, you are still fucked.
The fear factor of a roof full of ranged will mean that it will get mostly avoided until late into the round, which means that there might not be enough shielders left to effectively counter the rangedroof, which is very problematic even with multiple shielders. Even if you jump through many hoops to make ranged on roofs less problematic, ignoring the problems that indestructable ladders could cause, the question still remains. Why should ranged be allowed complete immunity from cav and relative immunity from infantry?
