How bad is this? (urgent) Roof

I would wash the roof like others have mentioned. Use a soft bristle brush, a car wash brush for example, and some non abrasive cleaner(roof cleaner). Do not use a pressure washer, nothing good can come of pressure washing a RV. Regular garden hose, water, soap, bucket and brush. There are coatings that you can buy to re seal the roof. I haven't used them myself. I would avoid using eternabond on the entire roof. I am up on my roof 2x a season, 1x at the beginning to check for any cracks in the caulking and once at the end to re-caulk and inspect. I have owned 4 trailers and have done this with every one. I am a big fan of dicor self levelling lap sealant. It's not extremely expensive and does the trick. If fact any monkey with a caulking gun can apply it. I have read that RV roofs are good for 12 years, however I have had an older unit that was meticulously maintained by the first owner and my roof was awesome never had an issue with it. Best of luck with everything.