I've noticed that there's plenty of information up about methods to get your bonus rolls, but not much about actually using them. Say I want Heroic Scales of Doom and I've already killed Butcher (Heroic) this week and used a bonus roll, only getting gold from that roll. I know that I can't run Butcher Heroic again (at least not before Tuesday) and get Scales via the traditional dropping route, but can I run it again specifically to use a bonus roll to potentially win it from the bonus roll?
I've searched around and couldn't find a clear consensus.