Yes, he begins by trying to make peace but becomes more aggressive as the dialogue goes on.
At the start of the dialogue, Romeo is focused on preventing violence and trying to maintain peace, urging Tybalt and Mercutio to refrain from fighting. However, after Mercutio is mortally wounded, Romeo's attitude shifts dramatically. He becomes filled with anger and seeks vengeance against Tybalt, indicating a transition from a desire for peace to a readiness for conflict and aggression.