What role did William McInnes play on NCIS: Sydney? Everything to know about his character

On NCIS: Sydney, Australian actor William McInnes plays the pivotal role of Dr. Roy Penrose, an Australian Federal Police (AFP) forensic pathologist. He is an essential member of the joint NCIS/AFP Sydney Task Force. Dr. Penrose is an expert in studying death and evidence scientifically. This work gives the agents—led by NCIS Special Agent Michelle Mackey—the important facts they need to solve difficult crimes involving US military members in and around Sydney.

About this character portrayal, in a 2024 interview with The New York Times, NCIS: Sydney showrunner Morgan O'Neill gave an idea that he was happy to have a dead body in the first five minutes and investigate it, just like the series has done many times before.

Everything to know about William McInnes's Character in NCIS: Sydney

In NCIS: Sydney, William McInnes plays the role of Dr. Roy "Rosie" Penrose. Dr. Penrose is an important forensic pathologist for the Australian Federal Police (AFP), working for a special task force that combines the investigative power of the American NCIS with the local law enforcement strength of the AFP. In this role, he is directly responsible for carrying out autopsies, studying physical evidence, and giving the forensic results that lead the investigations.

In an interview with The Sydney Morning Herald on February 6, 2025, William McInnes mentioned,

“Someone sent me a review about this thing, and they said the pathologist part is played by an Australian actor called William McInnes, who looks like the Bundaberg Bear come to life. Hasn’t he heard about the numbers – that the first episode in the US was watched by just under 10 million people, when broadcast and streaming numbers were combined. That’s huge!”

Dr. Roy "Rosie" Penrose is known for his blend of scientific brilliance and a curmudgeonly demeanor. While he may possess a dry wit and a sometimes-sardonic attitude, his sharp scientific mind is beyond question. He is one of the pillars of the NCIS: Sydney team, offering factual, evidence-based insights with an often humorous, uniquely Australian delivery.

Among his nicknames—"Rosie"—is one of the affectionate details that make him endearing to viewers. In the lab, he has a close relationship with the younger forensic scientist Bluebird "Blue" Gleeson. The friendly relationship and mentorship often bring touching and funny moments to the show's otherwise dark subject matter.

Dr. Penrose's main job as a forensic pathologist is to figure out how and why someone died. He often finds clues that the police missed. The NCIS: Sydney cases usually change when his scientific discoveries are used as evidence. But he is involved in more than just the lab.

He got directly involved in the action outside of the autopsy room in the first season of NCIS: Sydney. In a dramatic turn, he was even put into a hostage situation, showing that the character is willing to risk everything. In NCIS: Sydney, the character is shown as a down-to-earth person.

The character has a defined personal life outside of his work at the AFP and with the NCIS: Sydney Task Force, which makes him more complex. Alice Penrose is married to Dr. Penrose. He also takes care of his Terrier, Buster, seriously, which makes him a good dog owner. These facts about the scientist give the audience a better connection to him. 

NCIS: Sydney episodes are available to stream on CBS.