First I will give the simple list you asked for, then I'll be happy to give an explanation. Romeo has four mood swings in the time period you mention:
- Mood swing from love of Rosaline to love of Juliet
- Mood swing from love of Juliet to rage at Mercutio's murder
- Mood swing from rage to despair over consequences of Romeo's murder of Tybalt
- Mood swing from despair back to love of Juliet
Romeo has four definite mood swings in the first three acts of Romeo and Juliet, but only one of them is befitting to the swings of a "typical teenager." The first few of times we see Romeo, his mood remains steadfast: he is pining over Rosaline and bemoaning his own misery in love. Even when Mercutio appears on the scene and does his best to snap Romeo out of his rant, Romeo remains steadfast in melancholy even though he does agree to go to the Capulets' party. Therefore, Romeo's first authentic, total and complete mood swing happens the very second he lays eyes on Juliet, the proverbial "love at first sight" idea. Romeo's previous lines have been about death, but now his mood totally changes:
What lady's that, which doeth enrich the nad / Of yonder knight? / . . . O, she doth teach the torches to burn bright! (1.5.41-45)
Romeo makes his way to Juliet and they exchange their first flirtations of love. It isn't long before the two are married and Romeo is rejoicing in that sacrament. Even throughout the murder of Mercutio, Romeo uses his love for Juliet as reason enough not to fight Tybalt. Romeo's second mood swing begins the moment that Mercutio dies:
Alive in triumph, and Mercutio slain? / Away to heaven respective lenity, / And fire-eyed fury be my conduct now! (3.1.122-124)
In his rage, Romeo kills Tybalt. This is the only time, it seems, that Romeo's thoughts waver from that of his love for Juliet. Ironically, it is here that Romeo exclaims, "O, I am fortune's fool!" (3.1.137). Furthermore, the next time we see Romeo, his mood has changed for the third time (and rightly so), for he is considering the horrible consequences of his actions: banishment from Verona. And this, of course, turns him back to his love for Juliet (Romeo's fourth mood swing) as he rushes to her side to consummate the marriage.
In considering Romeo's mood swings, my conclusion certainly did not coincide with my hypothesis! Before doing my research, I thought for sure that Romeo, being a fickle teenager, would be destined to mood swing after mood swing. You know what? That's not so. He only has four mood swings in the first three acts. I was so surprised! Quite honestly, there is only one mood swing that befits the conduct of a "typical" teenager: the mood swing from Rosaline to Juliet claiming "love at first sight." The others are understandable. Who wouldn't have a mood swing as a result of his best friends murder? Who wouldn't reel at the consequences of committing a murder himself? And who wouldn't eventually shift thoughts back to his brand new wife? I don't care how old a person is, my thought is that everyone would be susceptible to the same exact mood swings as Romeo. The only exception is the complete switch of affection that appears in Romeo's very first mood swing. Ironically, I have always thought that Romeo and Juliet was all about intense infatuation, but in reviewing your question, I'm not so sure anymore. I'm not so sure that anyone who can remain that steadfast in love can be labeled as "infatuated."