The last soliloquy of Romeo after he has killed Paris functions as Romeo's last words in the play, where he comments on the destiny that has led him to this place and which has resulted in Paris' death too, the appearance of Juliet and his self-urging to take the poison and kill himself.
It is clear that when he realises who he has just killed, Romeo feels sympathy for Paris. He describes Paris as: "One writ with me in sour misfortune's book!", which shows that he sees Paris as another victim of fate, which throughout the play is seen to be a strong, implacable and impersonal force.
This speech also functions as a vital piece of dramatic irony. We, unlike Romeo, know that Juliet is really alive, and so it is intensely ironic that Romeo again and again refers to how life-like Juliet looks and his amazement that death has not claimed her and transformed her appearance:
Death, that hath sucked the honey of thy breath,
Hath had no power yet upon thy beauty.
Thou art not conquered. Beauty's ensign yet
Is crimson in thy lips and in thy cheeks,
And death's pale flag is not advanced there.
His ability to realise that Juliet is not actually dead is completely tragic, in every sense of the word, and the appearance of Juliet leads him to question whether Death is preserving her to be his lover. This cements Romeo's resolve to never leave this tomb again.
In contemplating his own death it is clear that he sees suicide as an escape from this world and from fate that has been so cruel to him and Juliet:
Will I set up my everlasting rest
And shake the yoke of inauspicious stars
From this world-wearied flesh.
Romeo is literally worn down by the oppression of fate (the stars) and his act of killing himself he sees as freeing himself from the dominion of fate.