Philippa Roet was the second daughter of Payne (Gilles) Roet of Hainault. She had an elder sister, Isabel, who became Chanoinness of the Convent of St. Waudru, Mons, by nomination of the Empress Margaret of Bavaria, sister to Queen Philippa of Hainault, wife of England's Edward III. Philippa's younger sister, Katherine, is the woman whose life is celebrated in Anya Seton's novel, Katherine, and is known to history as Katherine Swynford, the mistress and eventual third wife of John of Gaunt.

Philippa joined Gaunt's household in time for his c. 1372 marriage to Constance of Castile, whose father's violent life was later the subject of one of Chaucer's writings (O Worthie Pedro... of The Monk's Tale of The Canterbury Tales).

Philippa and Geoffrey's son, Thomas Chaucer , was one of the supporters of the new reign of Henry IV, Gaunt's son, who took the throne by force from his cousin Richard II. Together with his cousins, the Beauforts (offspring of sister Katherine and Gaunt), they formed an important role in solidifying Henry's government.

Philippa's pension was collected for the last time in c. 1386 and it is assumed that she died shortly thereafter.