It is not an emergency, just seat up the cleanout for now. When you have a safe time to get up on the roof in spring is soon enough. It will take removing the tee snout, pulling the liner up and adding the extension with a cap on it. Attach to bottom of the tee and reinstall.Or you can just cap the tee and vacuum it out after sweeping.
Wow! I have to admit, that sounds pretty involved! Is it something I can do if I'm pretty handy or should I have a professional do it?
With regard to seating/sealing the clean out, how would you recommend I do that? Juvenile question I know...