Using straight bleach is not recommended and scrapping you should avoid at all costs.
Go to a pool supply center and buy 5 gallons of Chlorine (SH) and go to home depot and buy Original Sent Gain (bright green bottle) detergent and a bleach approved pump sprayer.
In a 5 Gallon bucket mix 1.5 gallons Chlorine with 3.5 Gallons of water and 16oz of Gain.
Pour this into the sprayer and soak the roof. When I say soak I mean Soak! Everything will start to turn white and die off.
Let this dry and reapply in 2 - 4 weeks.
once everything is dead it will start to flake away.
At this point use a garden hose with spray tip to remove any moss.
I hope this helps.
Please let me know if anyone needs to know further details.