One interesting thing about Romeo's final soliloquy in the final scene is that it is full of expressions of irony, both situational and dramatic irony, that help capture the intensity and drama of the moment and the play as a whole. By noticing these expressions of irony, we can better see the drama of the scene and the play.
One instance of situational irony we see is that, after killing Paris, Romeo asks himself if he had heard his servant say that Paris was supposed to have married Juliet, as we see in the line, "He told me Paris should have married Juliet. / Said he not so? or did I dream it so?" (V.iii.78-79). The irony is that we can also interpret this line as a philosophical statement that Paris should have married Juliet instead of Romeo. Had Juliet done so, she would have been well-provided for by a good husband who loves her dearly, and she would have saved herself a great deal of grief and saved her own life. This final speech of Romeo's shows us that, ironically, Romeo is aware of this too, which helps capture the drama of the play by showing us that so much grief could have been avoided had the characters thought with more reason.
We can also see another instance of situational irony in the passage in Romeo's final soliloquy in which we see him regarding Tybalt's dead body. In this passage, Romeo looks at Tybalt's body and declares that he is about to kill himself with the exact same hand that took away Tybalt's youth, as we see in the lines:
O, what more favour can I do to thee
Than with that hand that cut thy youth in twain
To sunder his that was thine enemy. (98-100)
In this passage, the word "sunder" can be translated to mean "split," or "destroy." In other words, Romeo is telling Tybalt's dead body that he is about to do him a great favor by destroying his own self with the same hand he used to destroy Tybalt. It is ironic that the killer, Romeo, should now kill himself. This is an instance of situational irony because, of course, the reader was not expecting Romeo to commit suicide by Tybalt's side, which again captures for us the drama of the moment, showing us how all characters in the play are being punished for rash, impetuous, violent, passionate emotions.
We see an instance of dramatic irony in this final soliloquy when we see Romeo noticing that Juliet still looks beautiful and still has color in her face, rather than looking pale, stiff, and dead. We especially see this irony expressed in the lines, "Death, that hath suck'd the honey of thy breath, / Hath had no power yet upon thy beauty" and further still in the lines, "Beauty's ensign yet / Is crimson in thy lips and in thy cheeks" and, finally, again in the line, "Why art thou yet so fair?" (92-93, 94-95, 102). The irony is that Juliet is, of course, not actually dead and had Romeo realized this, he would have spared both his own life and Juliet's. This is an instance of dramatic irony because, of course, the reader is aware of things that Romeo is oblivious to. Romeo's oblivion creates further drama for the moment because of course the reader is aware that a great deal of agony could have been prevented had Romeo been thinking more rationally.