I glue aluminum foil, shiny-side out, to cardboard, wood, plastic, you name it. It looks nearly identical to one of those high-end dimpled reflectors(especially cardboard) or smoother(wood!) by the time I'm done. In practice they promote more even growth with less plant-stretching towards the bulbs, and I say they make bulbs about 1.7 times as effective. I wouldn't use a rolling pin. I use a soft cloth and moderate pressure, gives it a nice sheen. I've also used a sack of beads in a spandex, probably, it's a ergonomic wrist rest. It created micro grooves from the beads and the sheer material, looks interesting and would likely promote diffusion while not cutting as much intensity.
This 'Mylar' stuff people use is actually more specifically aluminum metalized (bonded) to PET(this is really Mylar, it comes in clear, matte, and other finishes/styles) fabric. Aluminum foil > plain/flat white paint any day. The only real spectral reflection measurements of white paint that I've seen where pretty bad without juicing the paint with raw titanium dioxide or raw magnesium fluoride. Flat white paint cuts intensity and creates diffusion. Aluminum (I don't care what kind) doesn't do this. It's an excellent reflector and 99% of commercial reflectors are (often coated) aluminum.