When doesn't Romeo act emotionally immature in Shakespeare's Romeo and Juliet?
The first time that Romeo is mentioned in the play—after the brawl in the streets of Verona between the feuding families of the Capulets and the Montagues—Romeo's friend Benvolio and Romeo's father, Lord Capulet, compare notes about Romeo's recent behavior.
Benvolio says that he just saw Romeo that morning, walking alone in the woods, but when Benvolio approached him, Romeo "stole into the covert of the wood" (1.1.121).
Lord Montague tells Benvolio that Romeo has often been seen in those woods "with tears augmenting the fresh morning's dew" (1.1.128).
Neither of them knows the cause of Romeo's behavior, but as Romeo enters the scene, Benvolio tells Lord Capulet, "I'll know his grievance, or be much denied" (1.1.153).
Within a minute, Benvolio deduces that Romeo is in love, which is apparently not an uncommon reason for Romeo's lovelorn, forlorn behavior.
Benvolio asks Romeo for the name of the woman who is causing Romeo so much sadness, but Romeo won't tell Benvolio her name. "I do love a woman," Romeo says, and that's about all that Benvolio can get out Romeo, except for Romeo's lengthy, glowing description of the woman.
Her name is Rosaline. Benvolio must have squeezed her name out of Romeo between the first and second scenes, because by then Benvolio seems to know her name and everything else about her. When Romeo and Benvolio learn that the Capulets are having a feast that evening, Benvolio knows that "At this same ancient feast of Capulet's / Sups the fair Rosaline whom thou so lov'st" (1.2.86-87).
Romeo, Benvolio, and a few other Montagues attend the Capulet's feast uninvited, which is where Romeo falls out of love with Rosaline and in love at first sight with Juliet at precisely the same moment in a scene in which Romeo and Juliet have barely nineteen lines of dialogue.
When the feast is over, Romeo decides to risk death at the hands of the Capulets by scaling the wall into the Capulet's orchard so he can get another look at Juliet.
Within another few minutes, Romeo and Juliet decide to get married on the next day, even though their families are deadly enemies and they know almost nothing about each other, except that they're hopelessly in love with one another.
In time—a very short time—Romeo and Juliet go to see Friar Laurence, who is having a difficult time coming to grips with the fact that Romeo no longer loves Rosaline, with whom he was desperately in love just yesterday, and is going to marry Juliet, with whom he seems to be even more desperately in love today.
Nevertheless, Friar Laurence marries Romeo and Juliet (act 2, scene 6), and it isn't long before Romeo kills Tybalt, Juliet's cousin, and Romeo is banished from Verona by Prince Escalus (act 3, scene 1).
Romeo rushes to Friar Laurence's cell, and in what can only be described as an incredibly immature adolescent tantrum, Romeo throws himself on the floor, "blubbering and weeping, weeping and blubbering," as the Nurse says, and threatens to kill himself (act 3, scene 3).
Despite the fact that Romeo has been banished from Verona under pain of death, Romeo spends the night with his new wife—in Verona in her bedroom in the Capulet's home—and barely escapes from the balcony window before Lady Capulet comes into Juliet's room.
When Romeo next appears in the play, he's in Mantua, and Balthasar tells him that Juliet is dead. Romeo mourns Juliet about ten seconds before he decides to kill himself at her side in her tomb:
Well, Juliet, I will lie with thee to-night (5.1.36).
Romeo just happens to remember an apothecary with a shop nearby, where Romeo hopes to buy a vial of poison. Even though it's a holiday—a holiday which is not explained in this scene or anywhere else in the play—Romeo manages to rouse the Apothecary, who is reluctant to sell poison to Romeo because it's against Mantua law, and the punishment is death.
Nevertheless, Romeo prevails on the destitute Apothecary to sell him the poison, to which the apothecary responds,
My poverty but not my will consents. (5.1.78)
Romeo hurries to Juliet's tomb, where he confronts and kills Paris. Romeo drags Paris's body into the Capulet's tomb to fulfill Paris's final wish, then Romeo lies next to Juliet. Romeo wonders why Juliet looks like she's still alive, even though she's lying dead in the Capulet's tomb.
After a few overwrought lines to Juliet, Romeo drinks the vial of poison, and, "with a kiss," he dies (5.3.120).
This is the last thing that Romeo does in the play, and he has yet to do anything that wasn't emotionally immature—except, perhaps, when Romeo decided not to fight with Tybalt, but that was right before Romeo killed him anyway for killing Mercutio.