You will find it EXTREMELY hard to get any info out of the power washing guys on this site. They all have an attitude about everything, and expect that you should know everything already. I left this site over a year ago because of this section.
With that said, the ladder saver nozzle (I picked one up locally here) seems to work very well for me with my machine (landa belt drive with 4.8 gpm pump at 3500 psi I believe it is). I can reach the eves of a 2 story house that has been lifted 6 feet up, so I would Imagine you could do some good with yours on single story houses. It will spray chemical, so my guess is lob your chemical up on the roof with it then rinse with it. I am no pro, nor do I do this for a living, but power washing is a huge part of the final clean my company does on houses after we raise them. I pretty much got zero help form anyone here, and learned by trial and error. I also found hat the countless coat tail riders for pressure tek did me no good either, as there is a local store here who sells everything for the same price or cheaper, and it doesnt need to be shipped.
Please excuse my rant, just thought I would fill you in on a couple things I have learned.