In "That's Not What They Call It In Amsterdam", Alan and Lyndsey take Walden out to dinner, where they run into Zoey and her date, Peter. After dinner, Lyndsey, concerned for Walden, decides to set him up with one of her friends. After various double dates with bad results, Walden decides to stay single for a while. He goes out to Pavlov's where he meets Rose, and after "saving" her from choking to death on a peanut, the two hit it off. This news shocks Alan. He tries to warn Walden about Rose, describing her tactics and history with Charlie, but Walden disregards them, as Rose explained everything to him. Alan remains suspicious of Rose, thinking she is out to get Walden and walks in on the two engaged in a bondage game, thinking Rose has manipulated Walden. At the end of the episode, Rose takes a video-call from Jake at the army base who admits that he saw it coming with her and Walden before he is put off when she implies she had been spying on him as well.
As a continuation from "That's Not What They Call It In Amsterdam", in "Ferrets, Attack!", After a few weeks in the relationship, Walden asks Rose to move in so they can spend more time together. The next day, however, Walden gets a call from Zoey, and the two go out for coffee, where Zoey confesses that she still loves Walden and wants to give the relationship another try. Walden agrees, but does not know how to tell Rose, as she has already moved in. That night, on the deck, Walden tells Rose about Zoey and that he wants to get back together with her. Rose seemingly understands and accepts the decision, though Walden noticed she knew Zoey's name but she covers it up. She leaves as Walden begins to feel comfortable, until Rose sends her ferrets to attack him. She later shows up at Zoey's place and makes it look like Walden knocked her [Rose] up.
Zoey confronts Walden about this, as Walden realizes that Alan was right about Rose all along, despite Walden telling Zoey the entire true story, she ends up leaving him again after finding out that Rose moved in. Later, Alan borrows Walden's car and is attacked by two of Rose's ferrets that she had planted in the car.
In "Advantage: Fat, Flying Baby", it is revealed that Kate's new investor is Rose, to keep her away from Walden.
In "Mr. Walden, He Die. I Clean Room.", Rose will reapear to help Walden when the liaison between Alan and Lyndsey puts him in danger. Walden is picked up by Rose in a taxicab, who claims that Walden is being followed. They escape before Walden can be shot by a hit man hired by Larry. The hit man tails them but Rose manages to evade him. Rose suggests that they lay low at a place that the hit man will least expect Walden to be. They check into a sleazy motel, whose manager lusts after Walden. Rose and Walden apologize to each other for all of the grief between them, and ultimately end up making out on the bed. She warns Walden, who she just finished having sex with not to get in touch with anyone or Larry will have him killed.