Since "Phase One, Complete", Alan and Rose have been good friends. In "The Salmon Under My Sweater", they start spending time together, and eventually share a kiss. But after this they decide to remain friends when Alan is put off by her words.
In "Above Exalted Cyclops", Chelsea sets them up, unaware of Rose's stalking/obsession with Charlie. While Alan is worried at first, he and Rose hit it off and eventually have sex. This continues and Charlie does not approve, but reluctantly gives them his blessing. Alan also disregards Charlie's warnings about her. Rose later gets clingy and follows Alan around. However, Alan stays with her because of the sex. After he tries asserting boundaries, she glues a model car to Alan's crotch, similar to Charlie after their encounter. At the end, Alan breaks up with her and is in pain after removing the car and realizes Charlie was right and admits he should have listened. The episode ends with Rose climbing over the deck, stalking Alan.
In "That Darn Priest", Rose discovers Alan's ponzi scheme and Alan discovers Rose's husband is a mannequin. She gives Alan $50,000 to keep his mouth shut. After Charlie's sudden death in Paris, Alan (along with Berta and Evelyn) knows she killed him, despite this, no one has bothered to call the police to investigate. In "That's Not What They Call It In Amsterdam", it is shown Alan has lost all respect for Rose, and is very scared of her. By this point, Alan has not seen or spoken to Rose since Charlie's funeral, and upon reuniting with her he says "You have a lot of nerve coming to this house", with Rose firing back, "As much as you do still living in it". Once Rose and Walden begin dating, Alan fears for Walden's life, and attempts to 'save' him from being murdered like Charlie but surprisingly, Rose has genuine feelings for him and appears to be harmless. However, once she and Walden break up she sent her ferrets (all named after Charlie) to attack Walden and Alan in retaliation.