Bleeding Scarlett is a challenge in Captain Scarlett and Her Pirate's Booty.
Unlike wild rakk hives, Roscoe wears blinkers that help to protect his eyes, thus reducing the likelihood of critical hits. A barrage of explosive or incendiary damage directed at the head can still slip in past the blinkers and help to hasten Roscoe's demise. As a large target, Roscoe is also vulnerable to weapons that trade accuracy for power.
Adventurers are well advised to be at least 5 levels above the Roscoe in order to defeat him in under a minute.