Roger Moore's French dialogue translates to: "Waiter, listen. The lady is requesting that you a mix of three parts rum, one part vermouth and a dash of Angostura (bitters). Mix with plenty of ice. ... Serve with a peel of orange. Oh, and waiter: The same for me." He's telling the waiter how to make a Rumhattan.
As Montreal is a mainly French Canadian city, Simon Templar orders to the waiter in the French language. Roger Moore is fluent in French.