Hi Chris,
He would be "Capitaine Pierre Joseph Romain Rochas, vicomte D'Aiglun" , the title of vicomte will be placed normally at the end refering to the terittory connected to his title, in this case the region of Aiglun in Southern France.
The same goes for example for "Général Gabriel Gaspard Achille Adolphe Bernon, vicomte de Montélégier". This Napoleonic Division General is connected by title to the region of Montéléger [without the i these days], also in Southern France.
greetings,
Jimmy