Research Notes:

Guillaume of Jumièges names “quinque filios et quatuor filias...Robertus et Hugo, Rogerius Pictavinus, Philippus et Arnulfus, Emma, Mathildis, Mabilia et Sibylla” as the children of “Willelmus Talavatius...filiam suam...Mabiliam” and “Rogerium de Monte-Gummeri”. Orderic Vitalis names “Rodbertus de Bellismo, Hugo de Monte-Gomerici, Rogerius Pictavinus, Philippus atque Arnulfus” as the five sons of “Rogerius [de Monte-Gomerici]” and his first wife. Orderic Vitalis names “Rodbertum...de Belesmia primogenitum filium suum” [referring to Mabile] and adds that "cujus crudelitas in diebus nostris super miseras plebes nimium efferbuit". "…Rogerus de Monte Gomeri…Robertus filius Rogeri de Monte Gomeri…" witnessed the charter dated to [1060] under which Guillaume II Duke of Normandy granted "Brenerias" to the abbey of Bayeux. He witnessed a charter for Saint Martin de Sées with his brother Roger, and a charter for Saint Aubin of Angers in [1060/62] without Roger, suggesting that the latter had died by then. "Rogerius comes…et sua uxor Mabilia atque suus filius Rotbertus" donated property to Notre-Dame de Bellême by charter dated to [1070/79]. Orderic Vitalis records the rebellion of Robert, son of King William I, and his departure from Normandy accompanied by “Rodbertus de Bellismo et Guillelmus de Britolio, Rogerius Ricardi de Benefacta filius, Rodbertus de Molbraio et Guillelmus de Molinis, Guillelmus de Ruperia”, dated to [1077/78], and their journeys during five years of exile.

He succeeded his mother in 1079 as Seigneur de Bellême et d'Alençon. "Roger ex Northmannis Northmannus son of Roger" donated property to St Martin, Troarn for the soul of "his wife Mabel lately deceased" by charter dated to [1079/82], subscribed by "Rogerii comitis, Rotberti filii eius, Hugonis, Rogerii, Philippi, Arnulfis [filiorum eius]". He rebelled against William II King of England in 1088, crossed to England but was besieged at Rochester Castle and in Jun 1088 forced to surrender. Orderic Vitalis records “Edgarus Adelinus et Robertus Belesmensis atque Guillelmus de Archis monachus Molismensis” as the advisers of Robert [III] Duke of Normandy, dated to [1089]. Orderic Vitalis records that “Rodbertus Belesmensis” built “Furcas...castellum et...Castellum Gunterii...super Olnam fluvium ad Curbam” and attacked all his neighbours, dated to [1090]. "Rotbertus de Belismo filius Rotgerii comitis et Mabilie" donated the church of Saint-Léonard de Bellême, built by "Willelmus attavus Rotberti", to Marmoutier, with the consent of "fratres ipsius Rotberti, Hugo, Rotgerius, Arnulfus", by charter dated 1092. Orderic Vitalis records that, after the death of his father in 1094, “Rodbertus...filius eius” obtained “totum feudum eius in Normannia”, adding that he was “crudelis et superbus” and committed “innumeras iniquitates”.

He succeeded his younger brother in 1098 as Earl of Shrewsbury after a payment of £3000. He succeeded his father-in-law in Oct 1100 as Comte de Ponthieu. Florence of Worcester records that "Scrobbesbyriensis comes Rotbertus de Beleasmo" rebelled against Henry I King of England in [1101], was deprived of all his honours and estates in England, and retired to Normandy. The Annals of Margan record that “Robertus comes de Belesmo” was expelled from England in 1102 “cum fratre suo Arnulfo”. Florence of Worcester records that "Rotbertus de Beleasm" fought with Robert Duke of Normandy against King Henry I at Tinchebrai in [1106], was captured, but later escaped and fled. He helped Helias de Saint-Saens protect Guillaume, son of Robert "Curthose" ex-Duke of Normandy, after Henry I King of England ordered the arrest of the boy. He was arrested in 1112, imprisoned at Cherbourg and all his lands and honours forfeited. He was imprisoned at Wareham Castle, Dorset from Jul 1113.

The Annals of Margan record the death “Kal Mai” in 1118 of “Robertus comes de Belesme”. The 1130 Pipe Roll records payments made "in libatione Robti de Belismo" in Dorsetshire, Wiltshire. This suggests a pension or maintenance in some form, although it is not certain that it relates to Robert de Montgommery Earl of Shrewsbury. ²