Final answer:
Mercutio is the character in 'Romeo and Juliet' who tries to distract Romeo from his infatuation with Rosaline and is best described as a thoughtful friend.
Step-by-step explanation:
The character who spends most of Romeo and Juliet trying to help Romeo get his mind off Rosaline, even after Romeo has fallen in love with Juliet, is Mercutio. Mercutio is a close friend to Romeo and is known for his wit and lively personality.
Throughout the play, Mercutio attempts to cheer Romeo up and encourage him to move on from his unrequited love for Rosaline. However, his efforts continue even after Romeo meets and falls in love with Juliet.
Mercutio's constant desire to see Romeo happy essentially makes him a thoughtful friend and fits most closely with the description of option 3) from the question provided.