There is no dedicated "barrel roll" move in Toy Story 3: The Video Game on Wii. The game doesn't map an aileron roll to any input.
The game is a 3D platformer/beat-'em-up, not a flight sim. Mobility is built around jumping, rolling, and character gadgets—not aerial acrobatics.
Master the dodge roll and each character's traversal toolkit. That's how you survive Zurg's forces.