I would describe Rowley as a childish , Self assured, innocent, responsible and friendly. Rowley is one of those kids you would trust.
In the Movie Rowley and Greg have tough times sauting threw a few  arguments.
Rowley has Protective parents who don’t really think Rowley and Greg should be friends because of Greg misbehaviours.
Rowley is known to be best friend with Greg. Greg and Rowley are two different Characters, Rowley Like to be himself and enjoy everything but Greg  is completely different from Rowley, Greg wants to be the best and be Popular and is a massive (Wannabe).

Even though Greg and Rowley have being friends for a long time it seem's that Rowley and Greg weren't meant to be together. They both have completely different personalities. Greg found out that Rowley wasn't normal he was still a kid, but Greg tried to get rid of Rowley as a Wimp to Cool, But that doesn't work Rowley just like to be him self and never change or matter how much people judge him.