I see what you mean?
What I would do then, I would use what I had and stick my ladder under my van, the ladder won't go anywhere, I wouldn't even trust anyone footing it for the complete Job, footers tend to get board and there mind wonders off, or like happened to me once they walked off without thinking to answer there mobile phone, have something secure, and don't take any chances.
If you can get your ladders upto roof hieght, use a stand off on the bottom section of the roof tiles, the tiles and the stand off prevent the ladder twisting, but as I say always secure the bottom with your car/van, or if your on soft ground drive some pegs in and tie off the bottom.