Sources

1) Source: Chancery: Inquisitions Post Mortem, Series I, Edward I "Roger de Mortuo Mari (Mortimer), the elder...Edmund his son, aged 30 and more, is his next heir...Milverton. Two parts of the manor (extent given) held of the inheritance of Maud his wife of the king in chief by the service of two parts of ½ virgate land."Dated: 5 November 1282 Evidences Roger as father of Edmund.. External Link
http://www.british-history.ac.uk/inquis-post-mortem/vol2/pp263-270 (Data from direct source)
2) Source: Chancery: Inquisitions Post Mortem, Series I, Edward I "Roger de Mortuo Mari (Mortimer), the elder...Edmund his son, aged 30 and more, is his next heir...Milverton. Two parts of the manor (extent given) held of the inheritance of Maud his wife of the king in chief by the service of two parts of ½ virgate land."Dated: 5 November 1282. External Link
http://www.british-history.ac.uk/inquis-post-mortem/vol2/pp263-270 (Data from secondary evidence)
3) Source: English Baronies: a Study of Their Origin and Descent, 1086-1327. Reference: Pages 6-9: Barony of Miles of Gloucester (Questionable reliability of evidence)
4) Source: MISCELLANEOUS COPIES of RECORDS FROM VARIOUS SOURCES "Mandate by Edw. I. to Geoffrey De Jenevile, justiciary of Ireland, (as former mandates had not been executed by James De Aldithe and Maurice FitzMaurice, late justiciaries,) to deliver the castle of Legh, with the third part of the possessions late of Maurice FitzGerald, deceased, in the barony of Offaly, to Roger De Mortimer and Matilda his wife, notwithstanding the King's grant to Thomas De Clare of the custody of said barony, as the King has learned by the record of Robert De Ufford, formerly Lieutenant in Ireland, and by the assertion of others, that FitzGerald held said barony of said Roger and Matilda, William De Cantelupe and Eva his wife, and Humphrey De Bohun and Eleanor his wife, daughters of Eva De Brewes, fifth heir of Walter and Anselm, the Marshals, by the service of 12 knights' fees, which were equally divided among the three sisters".. External Link
https://discovery.nationalarchives.gov.uk/details/r/0f6398dc-5d08-44ed-ba34-6efdc3181c10. Reference: MS 608, f. 29
5) Source: Chancery: Inquisitions Post Mortem, Series I, Edward I "John son of Alan, of Arundel... Isabel late the wife of the said John seeks in dower a third of the manors of Halthamstan and Rodington, co. Salop, a third of rents in Westdene and Sengelton, co. Sussex, a third of the manor of Borhunte, co. Southampton, and a third of two parts of four water mills in Swanburne and Arundel, against divers tenants (names given) who called to warrant Roger de Mortuomari guardian of the said John's heir". Dated: 1274. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol2/pp58-65. Reference: C 133/7/14 (Data from secondary evidence)
6) Source: Special Collections: Ancient Petitions "1) Mortemer requests that right be done to her and that she have restitution of the castle and manor of Bridgwater together with the issues from the time that they came into the king's hand...Edmund de Mortemer (Mortimer), late husband of the petitioner; Roger de Mortemer (Mortimer), son of Edmund de Mortimer." Dated: c1322. External Link
https://discovery.nationalarchives.gov.uk/details/r/C9106839. Reference: SC 8/62/3076 (Data from direct source)