Watch this video from This Old House to learn how to remove roof moss.
1 Slide a margin trowel under shingles to unstick them from the ones below.
2 Slide sacrificial zinc strip underneath the loosened shingles.
3 Secure the strip with roofing nails.
4 Apply a dab of sealant to every nail head and run a bead of sealant under each shingle.
5 Continue installing zinc strips across length of roof, end to end, leaving a 1/8 in. space between the strips.
6 To kill existing moss and lichen, make a cleaning solution of equal parts bleach and water.
7 Protect nearby shrubs and lawn with plastic tarps.
8 Spray the cleaning solution onto the shingles using a garden sprayer.