Roark's Onix was Roark's second most used Pokemon.
Roark's Onix was first used to battle Paul's Elekid and Chimchar in Shapes of Things to Come. It gained the advantage over Elekid due to its large size and immunity to Elekid's electric attacks. Elekid managed to paralyze Onix with Static but the Rock Snake Pokemon used Stealth Rock and finally Paul recalled Elekid and replaced it with Chimchar. The Fire Monkey Pokemon avoided Onix's attacks by using Dig and defeated the massive Pokemon.
Onix appeared again when Roark battled Ash, easily defeated his Turtwig with a single Double-Edge. It then battled Pikachu and won by unleashing a Screech technique that was so powerful that it blew Pikachu back into a rock defeating it.
Onix battled Pikachu a second time during Ash and Roark's rematch. During the battle Pikachu used a Thunderbolt that was powerful enough to actually hurt Onix, despite it being a Ground type. Stunned by Pikachu's incredible electrical power, Roark's reacted to slowly to form an effective counterstrike and Pikachu lunged forwards and smashed Onix with Iron Tail, knocking it out.
|Double-Edge||Shapes of Things to Come|
|Slam||Shapes of Things to Come|
|Stealth Rock||Shapes of Things to Come|
|Screech||A Gruff Act to Follow|
|+ indicates this Pokémon used this move recently.*|
- indicates this Pokémon normally can't use this move.
- Roark's Onix is the second member of its species to be affected by Ash's Pikachu's Thunderbolt, despite the fact that it should be completely immune to it. The first was Brock's Onix.
- In the games, Screech is used to lower the opponents defensive power but does not actually do any damage. However Roark's Onix' Screech is so powerful that it can actually hurt its opponents.