If I understand correctly, your term "g/m2" basically means weight per unit area of the finished product, which varies with the hickness of the material. Hence a roll made with g/m2 = 100 weights twice as much as a roll with g/m2 = 50, because the finished material is twice as thick, right?

Now does the "g/m3" nomenclature mean weight per unit volume? If so, the value of g/m3 is simply a property of the material itself, and not it's thickness. Doesn't matter whether you make the roll 1 inch think or 2 inches thick, the weight per cubic foot is the same. Consequently it's impossible to determine the weight of a roll made with a certain g/m3 unless you specify volume of material used, and that in turn means knowing its the thickness. Hence it's impossible to answer the question as presented. On the other hand - perhaps I don't understand correctly what "g/m3" means, so it would help if you define it a bit better.