Margaery Roxton is the eldest daughter of Lord Jonothor Roxton. She is known for being keenly intelligent and devoted to her family. She is three-and-twenty in 514 A.C.
Before the Blight, she was, surprisingly, a keen gardener. She is also known to be fond of her Uncle, Parmen Flowers.
Margaery travels from the Ring to Oldtown with her family to attend a Ball held by Lady Ashara Lannister. During the journey, she and her sister Jocelyn witness signs of their sister, Alicent's madness.
Whilst in Oldtown, she and her family dine with Olyvar Tyrell, and learn of his concern about Garth Bulwer. Margaery and her father join him in a plot to deal with the problem the Bull Knight represents.
Later, along with her sister, she was invited to serve as a Handmaiden to Melessa Tyrell. On the journey to Highgarden, whilst stopped at an inn, she voiced her hesitation about taking up the position. Her sister convinced her to try. After being kissed by Jocelyn, Margaery is confronted by the frank realisation that her sister was in love with her.
After her initial hesitation and speaking with Lord Olyvar on the matter, Margaery decided to take up the position as a Handmaiden to Melessa. However, due to misunderstandings, their relationship soured. It reaching near breaking point during a visit from a contingent of Dornish to discuss a trade deal. During the course of the first night, however, her relationship with her sister Jocelyn changed dramatically.