SAFEST way to get on roof...OEM ladder or extension ladder?

I have used a ladder and put it as close to the original ladder as possible and use the OEM ladder to hold on to. I plan on having my roof washed before my trip next week and my gdaugters boyfriend will be taking over for me. i can supervise from the safety of my bedroom window when the MH is in the driveway. I have a knee issue and given the right circumstances I could trip, enough said.