Hey there!
I can't provide a screenshot right now.. but this is just something people might not know. Not a exploit or so i believe.
You can bonus roll multiple times on the same boss and it might be intended but im just putting it out there.
1. Do the boss, you roll and then you can bonus roll.
2. Do the boss again and you dont get ANY loot but you can still bonus roll.
I did this to get the immerseus trinket very fast. Got it in two weeks and i was unlucky. Spent 4 bonus rolls + 2 rolls :P