Why is Friar Lawrence responsible for romeos death?

Friar lawrence is some what responsible for Romeo's death. Friar Lawrence gave the letter to Friar John explaining Juliet's plan to fake kill herself. But because of the plague (which was very common back then) Friar John was delayed and could not deliver the letter to Romeo in Mantua. Romeo found out from Balthasar that Juliet was dead (when really it was the poison and she was not dead). He then ran to the Capulets tomb to kill himself in order to be with her in heaven.