One thing I know for sure, moss on your roof is never a good thing!
If you are selling your home and you have moss on your roof, most appraisers will require it be removed before the sale closes. More importantly, it will shorten the life of your roof. So what is the best solution? I know it’s not a good idea to pressure wash your roof – it removes the granules which are there to protect the shingles. You also don’t want to scrape off the moss – you might inadvertently crack or break a shingle.
I’ve had at least 6 cases where diligent homeowners power washed their roofs and along with taking off granules – they took about 15 years off the life of the roof! I had moss on my roof and recently had it treated. The process takes awhile, the moss dies and then is washed away by the rain. I went online and did a little research. This website has a very good overview of different methods so if the time comes, you will be better informed.