Paul, I think the pictures tell a pretty good story. The sealer appears to still be effective in some areas, and weathered away in others. I wouldn't be concerned with the sealer at all. Softwash the entire roof and what's covered in fungus will come clean. Reading the info. on the sealer, I don't see anything that leads me to believe you could possibly cause any harm.

As a precaution, do a test on the tile before you take on the project.

The sealer appears to be for floors. There is a good likelihood that where there is still sealer that there may be some reaction to the bleach that may cause some flaking of the sealer from the surface. THOUGH I believe you will be OK and there is only about a 10% chance of this being an issue.

AC