The whole phrase is "Brown Russian Roulette." The meaning is taking heroin and a possibility that you will overdose and die just like russian roulette.
Buyer: Dude, can you BRR on this stuff?
Dealer: Hell no man!
Buyer than shoots dealer for being a dealing liar.
Dealer: Hell no man!
Buyer than shoots dealer for being a dealing liar.
by JamesTheN00b June 5, 2005