Robert A. Diekroeger, MD earned a degree of a Doctor of Medicine. Licenses and Affiliations. Robert A. Diekroeger, MD has been registered with the National Provider Identifier database since August 11, 2006, and his NPI number is 1326059379. Book an Appointment. To schedule an appointment with Dr. Robert A. Diekroeger, please call (404) 255-9100..