The death soliloquy Romeo speaks in the final act is paralleled with Juliet's final long soliloquy spoken in her room just before drinking the potion because both are death soliloquies in a sense. Romeo's soliloquy in Act 5, Scene 3 is a literal death soliloquy, meaning spoken just before he literally kills himself with poison, while Juliet's soliloquy is a figurative death speech in that she is preparing to fake her own death. Due to the parallels of these two speeches, there are some similarities.
One similarity is that both speak of fear though for different reasons. Juliet is very afraid of waking up alive in the tomb, as we see in her lines, "I have a faint cold fear thrills through my veins" (IV.iii.16). In contrast, Romeo's fear concerns his jealous feelings related to Juliet. Metaphorically, he is personifying Death and wondering if Death has taken Juliet because he is in love with her and wants her for a mistress. He further says that "[f]or fear of [Death taking her as a mistress] I will stay with thee / And never from this palace of dim night / Depart again" (V.iii.102-108). In other words, he is dying by her side to protect her as his wife out of fear that Death will take her as a mistress if he does not. Hence we see that one similarity is that both soliloquies speak of fear, but for very different reasons.
Another similarity is with respect to images. Both refer to the image of potions; also, both refer to the image of dead Tybalt lying in the tomb.