In 1808 he was made colonel of a regiment of "Veliti a cavallo" in the army of the Napoleonic Kingdom of Naples. In 1810, a French Colonel Durand seeking to reassign several of the best cavalrymen in the Duke's regiment to a new regiment of Cuirassiers Durand had been ordered to form, the Duke felt himself affronted at having his men stolen and challenged Durand to a duel over the transfer. The two men met on horseback in full uniform and charged each other with sabres twice before Roccaromana's blade cut a wound along his opponent's arm and the affair was ended in the Duke's favour. In 1812, he was appointed by Murat to be his Grand Equerry. He accompanied his king on the Russian Campaign where, during the retreat, he lost all fingers on his left hand through frostbite. Having driven off an attack of cossacks, Roccaromana and his cavalry formed for a time part of Napoleon's escort as the Emperor was taken in a sleigh back to Vilna ahead of the main army. He was present at Battle of Tolentino in 1815, where his only son, Ernesto, then aged twenty-two, was killed before him and Murat's army totally defeated.