I think that the death of Romeo & Juliet was the fault of everyone who became involved in either the relationship between Romeo & Juliet or the frustration that they had to deal with. The people I would blame most for this would be Friar Lawrence, the Capulets & Montagues, even Romeo and Juliet themselves, who were mostly to blame.

One person who was very much involved in the relationship between Romeo and Juliet was Friar Lawrence. Friar Lawrence tried to help both Romeo & Juliet by marring them in secret and hiding them when they needed. Although he tried, he failed more then once. Certain things that Friar Lawrence did only complicated the issue more. Like in Act 4 Scene 1, when he Tried to help Juliet by attempting to fake her death but didn't tell Romeo, despite his attempts. Another thing would be when he told Romeo to just go to Mantua...