Rochelle is the girlfriend of Spencer, Jess's cheating ex-boyfriend. She loves bikes, wearing funky hats, and singing along to the car stereo, all of which are things that Jess is known for. Her similarity to Jess clearly attracts Spencer, though he sees the two women as completely different people.
History
Pilot
Rochelle is first seen walking out of Spencer's bedroom in her underwear in New Girl's "Pilot" episode, only to find Jess, naked, standing in Spencer's living room. Jess is equally surprised to see her emerge from the bedroom she's shared with Spencer, and promptly breaks up with the man she dated for six years.
Jess moves into the loft two weeks after the break-up, but struggles to move on after Spencer's betrayal.
Kryptonite
Having lived in the loft for a few weeks, Jess is playing a game of basketball in the living room with the guys. She accidentally breaks Nick's TV and must finally confront Spencer to get back her remaining possessions, which have remained at his house since she left because she shared everything she owned with him. She tells the guys that she doesn't want to go back to see Spencer with his new girlfriend, whom he refers to as a "ho." But when she realizes that she's being unfair, she admits that she could be a "really nice ho."
She meets Spencer in a nearby park, but she's unable to convince him to give her back her things. She asks how his new girlfriend is, and he says that things with Rochelle are great, because they both really love bikes. Jealous, Jess thinks her name makes her sound like a mermaid, as she also loves bikes. She tries to ask Spencer when it would be a good time to get back her stuff, which she needs, and Spencer tells her that he needs something, too.
Unable to say no to him, Jess gets roped into driving Rochelle to the airport. Rochelle is polite, thanking Jess for the ride from the backseat before she and Spencer launch into an obnoxious rendition of "Bust A Move" together. Further, Jess promises, but does not follow through with due to the support of her friends, a spur of the moment promise to pick her up again from the airport the following Sunday.