That appears to be a good amount of water to just be a moisture issue. Is it the whole length of the roof or is it seem to be sticking to the front/back.or on one side or the other. Also is it constant issue or is it only during a rain after you have driven it or when its been parked or both. Not sure what your rig setup is so I'm just going to toss out some ideas. Front windshield seal is leaking, upper section of one of the door seals is drooping or out of place, roof rack mount is leaking. Also can't tell if you have a sunroof but those can also leak. Some of those issues may or may not be more apparent during driving or parked or how bad it's raining. Also if you do have a sunroof not only could the seal be leaking but most of them have a drainage tube that can become clogged allowing water to pool where you don't want it. My suburban used to leak before I sold it but only when it was raining and I was driving it. Back door seal at the top was drooping just enough to collect water but would only get pushed inside when I was driving.