Rose Moseby is Mr. Moseby's grandmother (also portrayed by Phill Lewis himself in a dual role), who appeared exclusively in the episode "A Nugget of History" from The Suite Life of Zack and Cody. She was once, fictionally, a dancer for Hugh Mulzac on the S.S. Booker T. Washington.
Not much is known about Rose Moseby's early life except for that while she was a young woman in the 1940's during World War II, she worked and performed as a dancer aboard the S.S. Booker T. Washington, after African-Caribbean American Captain Hugh Mulzac assumed leadership of the ship as the head of the U.S. Navy's first integrated ship crew with both Whites and African-Americans. She makes her first and only appearance as a one-time character in the episode "A Nugget of History" from The Suite Life of Zack and Cody, when she comes to visit her grandson, Marion Moseby, at the Tipton Hotel. Mr. Moseby himself, upon introducing her to Zack and Cody, remarks how he loves her a lot but considers her to be totally different and opposite from him, since she loves kids, is very affable, and has a goofy sense of humor.
In the episode, Nugget of History, after Rose meets Zack and Cody, she then becomes cordially acquainted with their mother, Carey, and agrees to go on a fun shopping trip with her while she's in Boston. Before they leave for the trip, the twins tell her and their mom about their project from their history teacher that requires them to write essays about "fascinating historical firsts from the 1940s." From there, Rose helps Zack with his project by suggesting to him to write about Hugh Mulzac and agrees to help him with the research for his paper. Days later, however, their history teacher, Mr. Dwosh, gives Zack a "D" on his paper, claiming that the facts in Zack's paper are inaccurate, and he also gives him a week of detention when Zack talks back to him, trying to defend his assignment. Outraged, Rose agrees to go with Zack to his school to give proof from her experiences working with Captain Mulzac to Mr. Dwosh, and to prove him wrong, and help persuade him to revoke the bad grade from Zack's paper and revoke the week of detention he gave him. After he apologetically agrees, he revokes his bad grade and his detention, and Zack thanks Rose for her help.
Rose Moseby, in a lot of ways, is the opposite of her grandson Mr. Moseby, because while Mr. Moseby is usually rather sharply irritable, stern, and quite urbane and refined, Rose is very down-to-earth, easy to talk to, and very friendly. Also, unlike Mr. Moseby, she loves kids, and even jokes his lack of love for kids by teasing him of his celibacy. However, in some minor ways, she is like Mr. Moseby because she can be quite snarky and sarcastic sometimes when people try to get on her bad side or offend her, and when she becomes angry, just like him, she can get very somberly assertive and forbidding. Nevertheless, she loves her grandson and is very nice to those who respect her and treat her kindly.
- She is portrayed by Phill Lewis, who also plays as her grandson, Mr. Moseby, in a dual role.
- She is one of the many characters in the Suite Life franchise who appears in only one episode and is a one-time character.
- When her and Carey are about to go on their shopping trip, she jokingly says "Oh yes, baby, we're going to shop 'til we drop!" Carey laughs thinking she is only joking and meant it figuratively, but Rose retorts saying, "No, I'm serious, I have a fainting problem!"
- She says "Pish-Posh!" as her catchphrase interjection just like Mr. Moseby.
- Rose carries around a very large tote bag purse, in which she carries a wide variety of items, both large and small. This includes a small portable vacuum cleaner, smelling salts (for her fainting problem), the ship anchor from the SS Booker T. Washington (it's not the real anchor but a large novelty keychain anchor), a baseball autographed by Jackie Robinson , and another smaller purse, in which she kept the historical document proving Hugh Mulzac's story to be true.
- She hints at the fact that she may have had a celebrity crush on Jackie Robinson when he gave her an autographed baseball bat in her younger days.
- Her age is unknown but she is an elderly senior citizen, so she is presumed to be at least in her 70s or 80s.
- It is unknown whether she is Moseby's grandmother on his mother's side, whom he always talks about, or his father's side. She does not mention Mr. Moseby's mother in the episode.
- She is also the grandmother of Mr. Moseby's older brother, Spencer, although she does not mention him in the episode.