Who were not involved in the deaths of the two lovers, Romeo and Juliet, in Shakespeare's Romeo and Juliet?

Whether directly or indirectly, all the personages of the tragedy Romeo and Juliet are involved in the deaths of the two lovers.

Even the Prince declares that all have been involved in the tragic deaths of the young lovers:

Go hence, to have more talk of these sad things.
Some shall be pardoned and some punished. (5.3.323-324)

Here is how the various characters have been involved in the deaths of Romeo and Juliet:

• In the opening scene, the servants of both the Capulet and the Montague households insult each other and renew the feuding which creates the tension that exists throughout the drama, a tension that eventually leads to the deaths of Romeo and Juliet.


• Tybalt and Benvolio become engaged as Tybalt threatens Benvolio with his sword drawn. Further in the play, Tybalt wants to kill Romeo at the Capulet party, he fights with Mercutio and Romeo, and is killed by Romeo, who is then banished from Verona, a situation which leads to tragic ends.


• Lord Montague and Lord Capulet come out to fight during the brawl in the first act. Lord Capulet later demands that Juliet marry Paris, precipitating Juliet's reactive actions that lead to her death.


• Benvolio inadvertently initiates conflicts because he urges Romeo to attend the Capulet party, where Romeo sees Juliet for the first time. If Romeo had not seen Juliet, he may not have every met her, and would still be alive.


• Mercutio has a temper that matches Tybalt's; their fight causes Romeo, who has just married Juliet, to try to intervene. Tragically, Romeo kills Tybalt, an act that leads to his banishment and, later, his receiving of misinformation about Juliet that causes him to purchase poison. 


• The Nurse acts as an intermediary for Juliet, arranging for Romeo to consummate the marriage with Juliet in her apartments. Further in the play, the Nurse encourages Juliet to marry Paris although she knows that Juliet is already married to Romeo. This action is part of what precipitates Juliet's drinking the potion which places her in the Capulet catacomb, the place where she later discovers a dead Romeo who has sought her. In her terrible grief, Juliet then kills herself.


• Peter, the Nurse's servant accompanies her when she meets Mercutio; however, he does not report to the Capulets the romance between Juliet and the enemy Montague. (His report may have changed the course of things.)


• Friar Laurence is probably the most responsible for the death of Juliet because he has taken upon himself to perform the marriage ceremony of Romeo and Juliet, he has given Juliet the potion to drink, he has said nothing to the parents of the lovers, and he has abandoned Juliet in the tomb where she awakens and discovers Romeo's dead body, a sight which leads to her suicide.


• Lord and Lady Capulet insist that Juliet marry Paris. Their angry reactions to Juliet's pleas alienate her from her parents, causing her to turn to Friar Laurence in her dilemma. His potion buys time, but places her in a fatal situation later on, a situation brought about because of the parents' insistence that she marry Paris. 
  Lord Capulet angrily rejects his daughter by fatally ordering her to go to the church on Thursday or "never after look me in the face." Similarly, Lady Capulet dooms Juliet: "I would the fool were/married to her grave."