Roxy Rocket is a former stunt double turned thrill seeking thief.
The villain Roulette lured Batman into Devil's Square so that the villian team Roulette had gotten together- Roxy Rocket, Riot and Dr. Phosphorus- could take Batman out while Roulette booked bets on the outcome. It worked. However, Steph and Damian came to save Batman.
Steph spotted Roxy honing in on Dick, and she ejected herself from her vehicle to jump onto Roxy's rocket. She said, "Mind if I cut in?" while punching Roxy in the face. Roxy yelled, "Sorry, sweetness, but this rocket was built for one!" and Steph said, "Let's see what we can do about that!"
Stephanie managed to hijack the rocket while fighting with Roxy and direct it toward Dr. Phosphorus, who had a chokehold on Damian. Steph and Damian jumped clear, Roxy was not so lucky and got taken out of the game along with Dr. Phosphorus when her rocket collided with the radioactive man.
Find out more about Roxy here