You are doing a wise thing by checking to make sure there are no gaps or cracks in your roof caulking. Use Dicor Self Leveling Lap Sealant for the flat (or mostly flat) roof surfaces. You should also go around the rest of the trailer exterior and re-caulk any cracked or missing caulk. GE exterior white silicone is a good caulk for that. Check around any windows, light penetrations, etc. to see if there are any signs of leakage. Windows have to be re-sealed periodically, which involves removing the window and replacing the butyl tape, re-installing the window, and then caulking around the edges. You will want to ensure the weep holes at the bottom of the windows are kept clear as well. And I have one more extremely important piece of advice for you: Dump the Seahawks, GO COWBOYS!!!