Is it lust that leads to their death?

This is similar to a question that may come up in my exam and I would just like to ask a few questions.

In some ways I can see that Romeo's desire for Juliet is destructive: 'These violent delights have violent ends'.
But, is it more likely that Romeo and Juliet actually were truely in love? I was thinking I could compare Romeo's Petrarchan longing for Rosaline to his sincere desires for Juliet: 'exchange thy love's faithful vow in mine'.

I am comparing Romeo and Juliet to Shakespeare's sonnet and their portrayal of whether lust leads ultimately to death, if that helps!