as soon as someone mentions ladders and tree work I cringe, same goes with doing tree work from a roof, the only time im gonna be on a customers roof is to blow debris off after a job, and if the tree is currently inside the roof, too much liability when you start doing anything you dont have to, imo roofs are more dangerous than a tree
and, for me, if a ladder is coming out, its to bypasss something at the base, then it gets moved out of the way
of course, this can all change and rules will be bent, but its up to you and using your brain to make the decision, %100 you, when it comes to something like this, I may input my idea on how to do it safer, but im not gonna tell you that you HAVE to do it my way, so far nobody has gotten hurt working from my methods, but, that can change in an instant, and somebody could get hurt or killed
sorry for the little rant, just showing my way of handling that situation (Which would end up with a climb line installed with or w/o ladder)