Romeo: External Conflict
One should not let their emotions control them.
Act 3, Scene 1
Romeo is speaking to Tybalt because he is angry about Tybalt killing Mercutio. Romeo's anger fuels his will to fight Tybalt, and since Romeo does and Tybalt dies, Romeo must flee Verona, This is a major issue since Romeo is also forced to leave his wife, Juliet.
Act 5, Scene 3
Romeo is warning Paris, but Paris decides to challenge Romeo. Due to Romeo's desperate nature towards the end, he becomes reckless, and therefore kills Paris. The battle between Romeo and Paris causes Paris' servant to call the watch, and that causes even more issues.
Act 2, Scene 2
Romeo is assuring Juliet that he won't be caught and die while visiting her. Here Romeo takes a huge risk by going to see Juliet because of the chance of death. Sadly Romeo doesn't care since he "loves" Juliet that much before really knowing her.
Romeo's feelings for this lady that he's never met starts the whole conflict throughout the story, and also leads to their deaths. Romeo didn't think, but rather he let his emotions blind him of common sense.