Our roof is flat also on our Rockwood and have had no problems. The bed room is in the front of the camper and when we set up for camping my wife likes the front of the camper elevated just a little so there is no problem with water run-off. Now you ask your self why she likes it elevated ???? well I better clear this up now because I know where this could end up.
when the camper is level and I know it is, she fells like she is sleeping on her head and the funny part is she uses two pillows, you got me !!!! I set the camper on the high side of the level mark, so I am still in range.
If she likes it, I love it, it works. My wife sleeps well and the water runs off.