i would experiment a little... i'd start with whatever grease i had on hand. if it works, i'd forget about buying anything else. if not, i'd try something the was a little more heat tolerant. i'm sure they can be found locally. or you could wait for a while as i see that the Euro is weakening against the dollar.
i use that blue stuff i can buy a pint of at Ace Hardware for about five bucks in my coaster brake hub. i readily admit i don't even have a clue if a roller brake hub requirements differ. with my coaster, i avoid the eight mile 6% decent of the local mountain, as i think i have a pretty good idea of what kind of heat that would create.
edit: i did a little reading...
so metal to metal brake shoes similar to my coaster brake. i'm pretty sure i would never spend anything like forty dollars for 100ml of grease.
so i stand pat with my original recommendation.