Robert was the son of Reynold Rich, a merchant of Abingdon in Berkshire, and his wife, Mabel. Most famously, he was the younger brother of St. Edmund of Abingdon, the Archbishop of Canterbury. The family lived in what is now St. Edmund's Lane but, when Reynold decided to enter a monastery, Mabel sent these two sons to study for BA degrees in grammar at Oxford and then to be further educated in Paris, the two places being closely associated in those days. However, their pious mother felt it inappropriate to provide them with their living expenses, so that the two lads found themselves obliged to beg for food and accommodation. The next few years of Robert’s life were spent studying in Paris, until he attained his MA.

By 1217, Robert was back in England, being a clerk in the service of Stephen Langton, the Archbishop of Canterbury elect. He seems to have had rather a hard time in his early career for, three years later, in consideration of his services and sufferings, as reported by Cardinal Gualo of S. Martin's, the Pope granted him a license to hold an additional benefice. By 1225, he had been appointed the Rector of Bocking in Essex, but, around 1232, had transferred to Wingham in Kent. He seems to have held this living until his death, along with Prince's Risborough in Buckinghamshire.

In 1233, Robert's brother was appointed Archbishop of Canterbury. Within four years, the younger brother had become a member of the Archbishop's inner familia. He stood as Edmund's chief representative in England during the absence of the latter abroad in 1237-8 and, again, in 1240; and acted for him in regard to his dispute with the monks of the Cathedral Priory at Canterbury (1239). The attribution to him of authorship of one of the lives of his brother, St. Edmund, cannot, unfortunately, be sustained