With proper preparation even a weak character has an almost guaranteed chance of killing Bullroarer, if you meet him at a distance (across a lighted room). An unenchanted longbow does 7.5 damage/shot with ordinary (unenchanted) arrows. However, flasks of oil do 7HP nominal damage when thrown, and do triple damage (21HP) vs fire-vulnerable monsters. Bullroarer has 60 HP, so even a small stack of oil will finish him off.