Dry scraping can be done and you can also use chemical cleaners and killers to remove the lichen from the roof.
How to get rid of lichen on roof tiles.
Mix the solution directly into the sprayer rather than the bucket if you have a garden sprayer able to.
How to apply wet forget outdoor.
How to remove moss lichen from the roof with vinegar.
Use a stiff brush such as a pushbroom to scrape away any stubborn mold or lichen patches.
Fill a bucket with 1 gallon hot water.
However do bear in mind that you may also be causing chemical harm to the roof shingles.
After the second.
Dilute 1 part wet forget outdoor to 5 parts water in a pump up garden sprayer.
Once applied the wet forget starts to work on the surface and then over time will remove the dead lichen with exposure to the wind and rain.
To apply thoroughly saturate the surface with the wet forget outdoor cleaner.
Add 1 cup chlorine bleach 1 cup liquid laundry detergent and cup trisodium phosphate.
Natural and non toxic vinegar safely kills problem growth without filling your environment with toxic chemicals.
Wait 15 minutes and then repeat the application a second time.
In addition to rotting and possibly damaging your roof.
If your roof is completely or more or less completely covered in moss algae or lichens it is probably better to have your whole house re roofed.
Make sure no rain is in the forecast that day.
Clean up any organic matter on the roof such as twigs leaves or other debris.
Dip a brush broom in the diluted vinegar and scrub lichens off the roof tiles.
Once diluted thoroughly saturate the lichen or moss covered surface.