Casting director Ros McWilliams played a pivotal role in shaping the character roster of the James Bond franchise, specifically in selecting actors for key roles such as villains, M, Q, and Moneypenny. Among her notable casting decisions was choosing Danish actor Mads Mikkelsen for the role of the antagonist Le Chiffre in the 2006 film *Casino Royale*.

Although a French actor was initially favored for the role, McWilliams faced resistance from American studio executives who expressed concerns about the actor's accent, despite his preparation with a dialogue coach and screen tests. Determined to cast the right actor, McWilliams had already been monitoring Mikkelsen's work and saw potential in his performance range. When she learned he was nearby during production in Prague, she secured an immediate meeting and cast him on the spot. The director, Martin Campbell, quickly welcomed Mikkelsen to the set and introduced him in character, thrusting the actor into his role without delay.

McWilliams also addressed the casting of Eva Green as Vesper Lynd in *Casino Royale*, describing it as a contentious choice. Despite internal doubts from others on the production team about Green's experience, McWilliams advocated strongly for her casting. Green underwent two screen tests before finally earning the part. While McWilliams praised Green’s portrayal, she noted that the costume and hair departments seemed to attempt to age her character beyond what she believed was necessary.

Through these casting decisions, McWilliams demonstrated a commitment to talent and range, shaping some of the franchise’s most memorable supporting roles and villains. Her selections contributed to defining the fresh tone and character dynamics introduced in *Casino Royale*, influencing the series’ direction in the years that followed.