Executive Team

Richard Hammett CEO
Richard Hammett, Chief Executive Officer

Richard Hammett is the Chief Executive Officer of The Medical Center of Aurora (TMCA) and Centennial Medical Plaza (CMP). Prior to joining TMCA/CMP Richard was based in Austin, TX at St. David’s Medical Center where he served as Chief Operating Officer (COO) from 2007 until 2012, and as Senior Vice President of Strategic Planning and Development from 2004 to 2007.

Richard began his health care career with The Baptist Hospital of East Tennessee where he held several key roles from 1994 until 2004, after which he joined HCA and St. David’s. He has received his Bachelor of Science in Business, a Master of Business Administration and a Master of Science in Health Administration, all from the University of Alabama.

Richard has served on many boards and is an active participant in the community. His involvement and passion lie in partnerships with the Alzheimer’s Association, Big Brothers/Big Sisters, the American Heart Association, the American College of Healthcare Executives, and other mission based initiatives.


Bryce Dehaven


Bryce Dehaven, Chief Financial Officer

Mr. Dehaven is the Chief Financial Officer at The Medical Center of Aurora; including its Main Campus, North Campus, Centennial Medical Plaza and Saddle Rock ER. He has nearly 30 years of financial leadership experience in the healthcare industry. Prior to joining TMCA/CMP in 2013, Mr. Dehaven served as CFO to Orange Park Medical Center, a 297-bed facility in Jacksonville, Fla. Before relocating to Florida, he was CFO to 3 hospitals in Independence, Mo. and San Jose, Calif.

Mr. Dehaven completed his undergraduate studies at the University of Arizona, and received his Master in Business Administration (MBA) from the University of Colorado at Denver.


Dianne McCallister


Dr. Dianne McCallister, Chief Medical Officer

Dr. McCallister joined The Medical Center of Aurora as the Chief Medical Officer (CMO) in 2013. She provides medical leadership to The Medical Center of Aurora's Main and North Campus, as well as Centennial Medical Plaza and Saddle Rock ER. 

Prior to joining The Medical Center of Aurora, Dr. McCallister served as Chief Medical Officer and VP Patient Safety and Quality Systems for Porter Adventist Hospital in Denver. Before entering into these leadership roles, she practiced as a partner in large Internal Medicine groups in the Denver area.  Additionally, she served as Chief Medical Resident at Presbyterian/St. Luke’s Hospital and as an instructor in Internal Medicine for University of Colorado School of Medicine.

Dr. McCallister is a board certified Internal Medicine physician, with over 25 years of clinical experience. She holds an MBA from Denver University and is certified as a Green Belt in Six Sigma Process Improvement Methodology. 


Ryan Simpson COO


Ryan Simpson, Chief Operating Officer

Mr. Simpson has been in hospital executive roles for 15 years and is currently Chief Operating Officer for HCA/HealthONE's Medical Center of Aurora; including its Main Campus, North Campus, Centennial Medical Plaza and Saddle Rock ER. Having started this role in June 2011, he is responsible for the daily operations of these facilities.

Prior to joining HealthONE, Ryan served in HCA's Nashville market as Chief Operating Officer for The Sarah Cannon Cancer Center and TriStar Oncology Services. Prior to this he was with Baptist Health System of East Tennessee in Knoxville, and then Middle Tennessee Medical Center (MTMC) in the chief operations role.

Ryan graduated with a B.S. in Finance and Marketing from Birmingham-Southern College, and then received his MBA and a Masters in Health Administration from the University of Alabama at Birmingham. He is a Fellow in the American College of Healthcare Executives (FACHE) and is currently a board member of the Aurora (CO) Chamber of Commerce.


Erica Rossitto CNO


Erica Rossitto, Chief Nursing Officer

Erica Rossitto, RN, BSN, MBA/HCM joined The Medical Center of Aurora as Chief Nursing Officer in November 2013. With over 10 years of nursing leadership experience, Erica oversees clinical and quality strategies for The Medical Center of Aurora and its campuses: North Campus, Centennial Medical Plaza and Saddle Rock ER.

Erica came to The Medical Center of Aurora from North Suburban Medical Center (NSMC), a HealthONE facility, where she served as CNO for 5 ½ years. Prior to her role as CNO to North Suburban Medical Center, Erica served in various nursing leadership capacities in the HealthONE system and in Louisiana.

Originally from Louisiana, Erica is a Registered Nurse, having received a Bachelor of Science in Nursing with a Minor in Psychology from McNeese State University in Lake Charles, Louisiana, where she graduated Cum Laude. She earned her Master of Business Administration/Healthcare Management from University of Phoenix in 2006.