Will that ladder and roof hold a 300-pounder?

I don't know how you can maintain your roof without climbing the ladder and walking or crawling on top. I would do several things first. Test the ladder on the bottom rung by standing on it and bouncing slightly on it. If it looks like too much flex and feels unsafe to you I would put a brace from the ground to the bottom step made from wood that would eliminated the vertical load on the ladder attach points. Once on top if you crawl on all 4's you would spread the weight over a larger surface area. Also several shts of plywood can be placed where you need to work or inspect to help distribute the load. Good luck and let us know how you make out or at least post a Youtube video.