If ur just putting it on the roof ur not going to c 2 much diff, without doors rear hatch, etc ur return will be min. Try putting the fabric installation on top of the sound deadener, the stuff isn't for insulation as there is no air space in the material to allow for insulating. U would have to get a diff type of material to go over what u added (look up "second skin"), I'm using the padding off 3 diff rear cargo carpets for said (probably help minimally) and it also helps with sound when doing the thump tests u can heard a lot off diff between just the sound shit and sound plus carpet.

a lot if the sound deadener is more about a cleaner sounding music in the vehicle from what i've been reading