What quotes show that fate is to blame for the deaths of Romeo and Juliet?

Shakespeare announces in the Prologue that Romeo and Juliet are ill-fated because of the unfavorable position of the stars and that they will ultimately commit suicide: "A pair of star-crossed lovers take their life." In Act I, Scene 4, even before he meets Juliet, Romeo suggests that fate is about to intercede in his life. After Mercutio's Queen Mab speech, Romeo says, in an aside,

I fear too early, for my mind misgivesSome consequence yet hanging in the starsShall bitterly begin his fearful dateWith this night’s revels, and expire the termOf a despisèd life closed in my breastBy some vile forfeit of untimely death.

Romeo worries that fate has already determined an "untimely death" for him and that attendance at Capulet's party is the beginning of the end. He is, of course, correct. Once he meets Juliet, his fate is sealed as a series of events are put into motion which end at Capulet's tomb with the two young lovers dead on the floor. 
 
Fate is also invoked in Act III, Scene 1 when Mercutio unleashes his "A plague a both your houses" rant. Because he is a victim of the feud between the Montagues and Capulets, Mercutio, in his dying breaths, wishes misfortune on the two families. Romeo acknowledges this fate later in the scene when, after impulsively killing Tybalt, he admits, "O, I am fortune's fool."
 
In Act V, Scene 1, Romeo again nods to fate after he learns Juliet is supposedly dead, saying, "Is it e'en so? Then I defy you stars." He seems to suggest that fate had wanted to keep him alive to suffer, but he will defy this fate by buying poison and going to the tomb to die next to his love. Unfortunately, this seems to be what fate (and Shakespeare) had in mind.