Romeo's initial reaction to Juliet's "death" is disbelief, followed by anger. He curses the heavens, "Is it e'en so? Then I defy you, stars!" (Act V, scene I, l. 24). After checking and rechecking with Balthasar to be sure he hasn't missed something ("Hast thou no letters to me from the friar?" (V,i,l. 31), he decides exactly what to do.
He decides to write a suicide note explaining the entire situation, then searches for poison so he can kill himself next to Juliet's "dead" body. He finally finds poison at the house of a poor apothecary, and after convincing him to take his money, is on his way to the Capulet monument: "Come cordial and not poison, go with me/To Juliet's grave; for there must I use thee," (V, i, l. 85-86).
At the monument, Romeo encounters Paris, (who is there to grieve over Juliet's "death"), and warns him to get out of his way: "Good gentle youth, tempt not a desp'rate man. /Fly hence and leave me," (V, iii, l. 59-60). Paris refuses to leave, fearing Romeo has come to desecrate the bodies, and after a brief struggle, Romeo slays Paris.
Once inside the monument, Romeo takes his time looking over and enjoying the face and beauty of Juliet, remarking that she is still so lovely, even after "death." "Death, that hath sucked the honey of thy breath, Hath had no power yet upon thy beauty," (V, iii, l. 92-93). He assures her that he will never leave her side, then drinks the poison, toasting her in the process, "Here's to my love! O true apothecary!/ They drugs are quick. Thus with a kiss I die," (V, iii, l. 119-120).
Shakespeare conveys loss in different ways, for there are different types of loss throughout the play. Nurse's loss of her only child and dear husband are expressed as a natural chain of events. The loss of Mercutio is frantic and chaotic, as it is the driving force for Romeo's banishment. The loss of Tybalt is conveyed as a heartbreaking devastation for Lady Capulet (as their relationship seems a bit skewed to begin with), Nurse: "O Tybalt, Tybalt, the best friend I had!" (Act III, ii, l. 61), and Juliet, who is torn between feeling sadness over the death of her cousin and remorse over cursing her husband for killing him. The loss of Juliet is perhaps the most poignant, because it is truly devastating to Lord Capulet, Nurse, and Romeo. So much so that Romeo kills himself as a result.