spotted this on an sum1's site (american i think) http://store.goldenroseflowers.com/servlet/Detail?no=2

just a guess, but I would say they have sprayed with the glue over the top and dipped the heads into glitter,, then maybe used the glitter spray to dust over the rest of the rose, The build up of glitter on the tops of the rose could only have been done by dipping.

Could be worth emailing the shop and asking what they use.