Get some Eternabond tape and tape up every seam on the roof. I did that and will be doing that on every RV or camper I ever own from now on. I didn't have a leak, but my brother did so it scared me into doing this. I did a video on it (see below).
BTW, my brother's leak turned out to be the yellow marker light on the nose cap. He initially though it was the side window, then he thought it was the seam where the roof and cap meets and finally figured out it was the marker light. So check everything and seal it whether it needs it or not.