Roberta Day Quimby is the youngest daughter of Robert and Dorothy Quimby, and the youngest sister of the Quimby girls. She is a newborn baby at the end of Ramona Forever. She is about a year old at the end of Ramona's World, making her nine years younger than Ramona and fourteen years younger than Beatrice.
Roberta Day Quimby is the youngest Quimby and child. She was born in Ramona Forever. Her parents thought she would be a boy, but when she was born a girl they named her after Robert Quimby, the girl's father, naming her Roberta.
Not much is known about Roberta as she was a baby during the entirety of the Ramona and Beezus universe.