I too have found the roof top stuff inside the flaps. I'm considering getting a folding ladder from AMZN as seen in the picture. I did come up with a solution on one of my camping trips, but I can't always depend on that method.
I had a freinds 14 year old sweep the back roof down before I closed up the front. He's skinny as a rail and was happy to help.
Now I just sweep down the side flaps when I open the camper up and then sweep the crap out later.