One similarity between both parting scenes is that both reference morning. Towards the end of Act 2, Scene 2, Juliet says, "'Tis almost morning; I would have thee gone," showing that she feels urgently that it would be safer for Romeo to leave now due to the lateness of the hour, but also that she regrets having to part from him. Similarly, in the later parting scene, morning plays a huge role. Romeo must leave before day break because he has been banished, and if he is still found in Verona he will be executed.
The motif of birds also plays a function in both scenes. In the first scene, when Juliet says she should want him to go because it is almost morning she also adds, "and yet no further than a wanton's bird," meaning that she only wants to let him stray as far as a cruel person lets his/her pet bird stray, because she is so fond of him. Likewise, in Act 3, Scene 5, Juliet and Romeo converse about birds. When Juliet sees that Romeo is about to leave, she says that, "It was the nightingale, and not the lark" they just heard. Also, when she finally becomes convinced that morning has broken, she declares,
"It is the lark that sings so out of tune, straining harsh discords and unpleasing sharps. Some say the lark makes sweet division; this doth not so, for she divideth us." (Act III, Scene v)
Hence in both scenes, the imagery of a bird is used to portray the couple's separation.
Another similarity is that death is spoken of in both scenes. In the earlier scene, Juliet says that if Romeo were her pet bird, she would accidentally kill him "with much cherishing," meaning that she would love and cuddle the pet bird, or him, so much that it/he would be crushed and die. Also, when Romeo first appears under her balcony, she warns him that her kinsmen would kill him if they discovered him, saying,
"The orchard walls are high and hard to climb, and the place death, considering who thou art."(Act II, Scene ii)
Similarly, death is frequently mentioned in Act 3, Scene 5. Romeo tries to convince Juliet that it is morning, saying, "I must be gone and live, or stay and die." Juliet later responds by telling Romeo to hurry out of the window by saying, "Then, window, let day in, and let life out." Hence, in both scenes, illusions to death serve as a motif to represent the couple's separation and even foreshadow upcoming events.