Depends where you live. If you live in Pacific Northwest, there isn't much
you can do to keep the moss off the shady portions of your roof.
I had a cedar shake roof and cedar gutters on the house when I bought it.
The zinc strip trick didn't seem to make much difference, if any. I just
get up there each year in early Summer with a stiff broom and brush the
loose stuff off. Keeps it under control. Next time, I will get a steel
roof and say goodbye to roof moss forever.
Good luck!