In Romeo and Juliet, is Romeo a stock character - and does he change?
I suppose Romeo begins as something of the stock lover, though I've always thought that everyone underestimates the complexity of his ideas about love. Normally the lover just sees love as something painful, or something for which they would die (the tradition of the courtly lover talking like this goes back even into medieval literature). But Romeo's ideas are more complex:
O heavy lightness! serious vanity!
Misshapen chaos of well-seeming forms!
Feather of lead, bright smoke, cold fire, sick health!
Still-waking sleep, that is not what it is!
This love feel I, that feel no love in this.
Dost thou not laugh?
Love is, for Romeo, a matter of contradictions. He can't sleep, and nothing "is.. what it is". He feels love, but he feels it by the absence of feeling traditionally "in love". As he suggests at the end, it's almost comic in its absurdity. No other lover I know of in literature uses such intellectually complex language about love. Though some people would tell you he's a "stock" character in that respect.
Does he change? Yes, undoubtedly. Something far more violent is revealed when he murders Tybalt - and then, his furious rages with Friar Laurence after his banishment, his murder of Paris at the tomb, and his bitter nihilism with the apothecary ("The world is not thy friend") all add up to an entirely unromantic character.
So I'd say he starts off looking like (though not actually being) a stock characters. And becomes more and more individual from there.