You could go through rocks but you may not if the solid and the building are the same, or/and the solid may make it impossible to target and cast on anyone.
I don't think they really can't find a map material that can't make one being able to play from that roof. Really, it's not rocket science if a mapper thinks of it a lot. Those are things that happen because they didn't think to cater for, not because it's impossible, if they want to do it.