Let see, you had the roof replaced 2 years ago and after discovering some water, they did some additional sealing but he problems still exist? All other indication was the job was done professional and they were unable to find any leaks when you returned to them?
If so, exactly where are you finding the moisture? On RV's just like a home, water can enter one place but not show visible signs until it migrates to another place. Is the moisture in the bedroom area, bath, wardrobe? Along the walls, seams, corners or just the floor?