Would you say Romeo is nonchalant?William Shakespeare's Romeo and Juliet

As the antithesis of nonchalance is perhaps how Romeo could better be described.  For, rather than being coolly unconcerned, indifferent, or unexcited, Romeo is involved in every scene in which he appears. Even in his depression over Rosalind in the first scene, Romeo reacts strongly to the news of the fray after which the Prince has pronounced penalties on future conflict.  Speaking in oxymorons, Romeo declares,

Oh, then, brawling love! O loving hate!/O anything, of nothing first create!/O heavy lightness!  serious vanity!/Misshapen chaos of well seeming forms!....This love feel I, that feel no love in this. (I,i, 149-154)

When Benvolio tells Romeo to "Be ruled by me, forget to think of her [Rosalind]," Romeo replies, "Oh, teach me how I should forget to think" (I,i,191-192)   Clearly, these lines show anything but indifference.

As he scales the wall surrounding Juliet's orchard, a most involved and passionate Romeo declares, "He jest at scars that never felt a wound" (II,i,1).  To the child of his mortal enemies, Romeo declares his love after Juliet warns him about the guards,

Alack, there lies more peril I think eye/Than twenty of their swords.  Look thou but sweet,/And I am proof against their enmity. (II,ii,71-73)

As Juliet turns back to her room, Romeo excitedly asks, " Oh, wilt thou leave me so unsatisfied?" (II, ii,125)  He perceives occurrences with a magnitude that is cosmic:  "Oh, I am fortune's fool," and "I defy you, fate!"   He forces open the tomb of Juliet in excited terms,

Thou detestable maw, thou womb of death,/Gorged with the dearest morsel of the earth,/Thus I enfore thy rotten jaws to open,/And, in despite, I'll cram thee with more food! (V,ii,45-48)

As he ponders death, Romeo remarks passionately,

How oft when men are at the point of death/Have they been merry!  which their keepers call/A lightning before death. (V,iii,88-90)

In Shakespeare's tragedy, Romeo and Juliet, Romeo's soul reaches the zenith of desire and delight, it falls to the nadir of despair.  Indeed, Romeo's nature is the antithesis of nonchalance.