How do I write a sonnet about Romeo's perspective of love?

If you are writing a sonnet describing Romeo's perspective on love, it is important to begin by noting the structural limits of a sonnet.

A sonnet is composed of three quatrains (stanzas composed of 4 lines each), followed by a couplet (a stanza composed of 2 lines). This makes up a total of 14 lines in your poem.

A Shakespearian Sonnet also follows a specific rhyme scheme:

abab cdcd efef gg

The poem should be in iambic pentameter as well.

Now that you know how to write a sonnet, we will focus on what the sonnet should address. Romeo seems to have a passionate, but fickle perspective on love. For example, he believes himself to be in love with Rosaline at the beginning of the play, but once he sees Juliet he immediately forgets about Rosaline! That's a pretty big change-of-mind. 

Romeo also believes his life to be incomplete without Juliet, so for him, love is the only reason for him to live. Once he hears that Juliet is "dead," he goes to get a poison strong enough to kill himself.

If I were writing this sonnet, I would write the first quatrain (4 lines) about his love for Rosaline. The next quatrain would be about him seeing Juliet for the first time, and forgetting about Rosaline. The third quatrain would be about his love for Juliet and how he does not want to live without her. For the couplet, or ending of the poem, it would be wise to summarize what you have said so far by characterizing Romeo as passionate and quick to change his mind.

Hope this helps!