It is important to remember that Romeo and Juliet are intended to be flesh-and-bone characters, even in Romeo's possibly sexual motives; but it is not impossible to see the clearly carnal aspects of their love for one another and still like both Romeo and Juliet.

First, we know that they are young teenagers. Juliet’s parents discuss her age in relation to her marrying. Her father says,

My child is yet a stranger in the world.

She hath not seen the change of fourteen years. Let two more summers wither in their pride

Ere we may think her ripe to be a bride.

Because none of the characters in the play who are aware of the growing romantic relationship between Romeo and Juliet remark on any inappropriate discrepancy in their ages, we can surmise that Romeo is not a great deal older than Juliet. Not surprisingly, as a teenager, Romeo responds to the young women around him with a growing awareness of their sexual allure. Therefore, Romeo alludes to this in his thoughts about his relationship with Rosaline. In fact, Shakespeare specifically introduces Romeo with the backstory of his unrequited love for Rosaline to let the reader know that Romeo is searching for love and anxious to find it with someone who will respond to him and return his feelings.

It is not so much that the chaste relationship Romeo has with Rosaline angers him because she will not enter into a sexual relationship with him, but it is her rejection of him that wounds Romeo. He is hurt. He recognizes that his love for Rosaline is unrequited. When Friar Lawrence asks Romeo if he has been with Rosaline, Romeo responds,

With Rosaline, my ghostly father? No.

I have forgot that name and that name's woe.

The "woe" he refers to is the pain that Rosaline's rejection of him caused. It is also important to remember that both characters are of marriageable age. In fact, when Capulet says that Juliet is too young to marry Paris, Paris tells Capulet,

Younger than she are happy mothers made.

Thus, although Shakespeare makes it clear that Romeo seeks a sexual liaison with a young woman who returns his amorous feelings, this search implies that Romeo seeks a wife, a life partner. His advances to Juliet include the arrangement for their secret marriage because Romeo sees his love for Juliet in romantic terms that encompass their spending their lives together.