After their arrival in his realm Charles the Bald rewarded the family defecting from his enemy by assigning to Robert the lay abbacy of Marmoutier in 852.

Robert's rise came at the expense of the established family of the Rorigonids and was designed to curb their regional power and to defend Neustria from Viking and Breton raids.

With the Bretons under Salomon he led the Frankish nobles of Neustria and invited Louis the German to invade West Francia and receive their homage.

Later that year, Louis the German reached Orléans and received delegations from the Breton and Neustrian leaders, as well as from Pepin II of Aquitaine.

[citation needed] In 862 Charles granted Louis the Stammerer, his son, the lay abbacy of Saint Martin of Tours—a worthy benefice but small in comparison with the kingdom he had received in 856, and lost in 858.

[citation needed] In 862 two Viking fleets converged on Brittany; one had recently been forced out of the Seine by Charles the Bald, the other was returning from a Mediterranean expedition.

In 863 he again defended Autun from Louis the German; he campaigned in Neustria in 865 and again in 866, shortly before his death, dealing with Bretons and Vikings ravaging the environs of Le Mans.

[citation needed] On 2 July 866, Robert was killed at the Battle of Brissarthe while defending Francia against a joint Breton-Viking raiding party led by Salomon, King of Brittany and the Viking chieftain Hastein.