Instructions
Open the in-game menu by pressing the "Tab" key. A list of all the game's items and tools will be shown.
Click "Thrusters" from the list. Increase the device's strength and assign the key you want to activate the item, which is typically a number on the keypad. Once selected, you may close the window, and the "Thrusters" will be selected from your character's crossbow.
Shoot the thrusters underneath one side of the vehicle, either to the left or right. You may shoot as many thrusters as you want, although you will want to keep all of the thrusters on only one side of the vehicle.
Press the thruster button to make the vehicle perform a barrel roll. If desired, you can sit inside of the vehicle while you perform the barrel roll.