Ronaldo has a very nerdy appearance. He has blond hair, wears glasses, and has a big head to show that he's smart. He tries to look cool by wearing a red and yellow hoodie (similar to Kick's jumpsuit), and black jeans with red boots. These clothes are perfect for when he does street racing.
Ronaldo is the science nerd of the series. He uses quantum physics and all sorts of smarts to aid in street racing which is his favorite hobby until he loses to Kick Buttowski in "Mellowbrook Drift". He despises Kick and Gunther and would do anything to see Kick kicked out of school forever. Ronaldo is also very judging as he loves to judge Kick's plans on how he will perform the stunt for when he builds or announces it. Ronaldo has a way of being a gloating winner too as he gloats when he wins an event such as street racing, usually by means of cheating. He also gets away with things by using the good ol' Dine n' Dash routine in "Stand and Delivery" which almost runs Gunther's family out of business. But all is good as Ronaldo does have a soft spot for Kick and teaches him how to beat an extreme game show that has never been beaten before in "Faceplant!".
It is shown that he is in love with Kendall in "Frame Story". Kick finds this out by accident when Ronaldo and Kendall go to the janitor's closet to talk about their love. He tries his best to impress Kendall, but at somepoint usually ends out horribly wrong, such as writing a love poem entirely in binary or being too brainy instead of being more extreme.
He and Kick are sworn enemies and they don't like each other. But there are several times where Ronaldo helped Kick in daring situations revealing he has a soft spot and friendship for Kick.He is another of Kick's and Gunther's frenemies.