Roger Mainwaring was born circa 1263 in England to William Mainwaring (c1235-) . He married Christian Birtles (c1265-) .
The History of the County Palatine and City of Chester: Comp. from Original Evidences in Public Offices, the Harleian and Cottonian Mss., Parochial Registers, Private Muniments, Unpublished Ms. Collections of Successive Cheshire Antiquaries, and a Personal Survey of Every Township in the County; Incorporated with a Republication of King's Vale Royal and Leycester's Cheshire Antiquities, Volume 1 by George Ormerod, Daniel King, William Smith, William Webb (sheriff.), Sir Peter Leycester, 1882
"Roger Mainwaring, son and heir of William, married Christian de Birtles, and had issue William, son and heir; and Joan, a daughter, married Robert de Fallybrome nigh Britles, by whom she had issue Robert, John and Roger, living 1342. This Roger died in the lifetime of his father; and Christian, his widow, afterwards married John de Byrun; and lastly she married Robert de Varnon, living 8 Edw. III. 1334."
Children
| Name | Birth | Death | Joined with |
| William Mainwaring (c1286-) | 1286 England | Mary Davenport (c1286-) | |
| Joan de Mainwaring (c1290-) | |||
Siblings
| Name | Birth | Death | Joined with |
| Roger Mainwaring (c1263-) | 1263 England | Christian Birtles (c1265-) | |