She looks like Sandy but appears older and looks chubbier. Unlike her relatives, she wears an old-fashioned diving suit.
Role in episode
She arrives to drop off her three daughters, Macadamia, Hazelnut, and Pistachio at Sandy's treedome. Rosy tells her younger sister while they promised for her to babysit a day later, Rosy figured that she came a day earlier. Rosy meets Sandy's friend SpongeBob and laughs off his words at her daughters' being angels. She then tells Sandy that she hopes they took good care of her daughters. Rosy then promptly leaves back home to Texas.
In the end, she is in Texas and is submerged in a pool, relaxing contentedly with her kids being away until she sees a submarine and knows what is about to happen when it crashes into her. Popping her head through the submarine, Rosy is greeted by her daughters who are all happy to see her again, while she is very displeased with their antics.
She shares her name with her great-aunt Rosie Cheeks, though their names are spelled differently.