While we won't be able to find any passages in Romeo and Juliet that specifically talk about friendship or the love shared between friends, there certainly are many passages that portray friendship. We especially see friendship portrayed through the interactions of Romeo, Benvolio, and Mercutio.
We especially see the love Benvolio feels for Romeo when we see Benvolio express such deep concern for Romeo's sorrows and state of mind. In the very first scene, Lord Mercutio begs Benvolio to find out what is troubling Romeo. Romeo answers by stating that he is in love with a woman who will not return his affections and tirades about how cruel and paradoxical love is, which arouses Benvolio's deepest sympathies. We see Benvolio expressing deep sympathy when Romeo asks if Benvolio is laughing at him, and Benvolio replies, "No, coz, I rather weep" (I.i.182). We further see Benvolio express his love and concern for Romeo when he begs Romeo to take his advice and stop thinking of Rosaline, and when Romeo refuses, saying that Benvolio can't possibly teach him to forget about Rosaline, Benvolio swears to himself, "I'll pay that doctrine, or else die in dept," meaning that he'll "prove [Romeo] wrong, or else die trying" (eNotes, 241). Since we see that Benvolio is so devoted to helping Romeo forget about Rosaline, devoted to the point that he would lay down his life for his friend, we see that Benvolio feels deep love for Romeo as his friend and cousin.
We can also see the love Romeo feels for his friend Mercutio the moment he becomes so furious that Tybalt has killed him and wants revenge. The significance of Romeo's feelings for revenge is that just a few lines ago he was refusing to fight Tybalt as Romeo knows they are now family through marriage. However, Romeo's feelings for Mercutio and rage over his death become so strong that he momentarily forgets his relationship with Juliet, his new connection to the Capulet family, and even forgets the prince's new law. We especially see Romeo's feelings concerning both Mercutio and his death in the lines:
Alive in triumph, and Mercutio slain?
Away to heaven respective lenity,
And fire-eye'd fury be my conduct now! (III.i.123-25)
Since these lines well portray Romeo's feelings of fury, they also well portray his love for Mercutio.