Resealing your roof is time consuming, but well worth the investment considering that if you don't you are most surely going to have a leak, and quite possibly ruin your roof, ceiling, floor, and the list goes on.
First of all, do it when you know you will have good weather, as you don't want to remove all your caulking, just to have it rain and then pour into your RV.
All caulking seams need to be removed of caulk, dirt , debris, oils. The large amount of caulking used around vents need to be inspected for cracking and deteriation. If badly deteriated, then remove and clean throughly.
Replace only with caulking made for rubber roofs. Nothing from Wal-Mart! No Snow either! The caulking should purchased from your local RV Dealer.
Once that job is done...now take a look at your windows!