The roof noise is a problem with all RVs. the Styrofoam used to insulate the roof does not offer much reduction to sound, because it is a solid medium and sound travels very well in solids. To reduce the noise level, there would need to be an empty air area, like the attic in a house, without that the falling rain can be clearly heard.
We have gotten use to the sound and it actually puts me to sleep. the real surprise is the pop from a pine cone or small branch falling on roof, that well get your attention.