He had facilitated the conquest of Normandy for the king of France by giving French troops passage over his lands; together with Juhel III de Mayenne and Hugues de Beaussay, he negotiated in Philip's name a two-year truce with the King of England.
In 1213 he accompanied Louis, son of the king, who took advantage of the truce with the English to fulfill the vow he had made to go for 40 days to fight the Albigensians.
The following year he was one of the peer counts who issued a verdict on the claims of Erard of Brienne-Ramerupt in the county of Champagne; he helped to thwart Erard's efforts and to preserve the rights of the young Theobald IV and his mother, the countess.
Then, in 1220, King Philip II bought Alençon from Robert's two sisters, Alix and Hélia.
The lands of Saosnois, Montgommery, Le Mêle-sur-Sarthe were given to Aimery II, viscount of Châtellerault, son of Alix d'Alençon.