I am embarassed

Howdy. If you have never washed it you may also have not done any roof maintenance to the seals etc. If this is the case I would avoid using a pressure washer as more than likely there will be seals that are cracked and although rain may not have penetrated a pressure washer will probably cause water incursion. Consider a soft spray with a garden hose, soap and water and a soft broom to clean it up. After it is dry take a close look at the seals and reseal where required. Try to look at them once per year.

Be careful up there and good luck.