Brigadier General Guillermo Rosales Jr. was born in Mexico and raised in Chicago, Illinois. He earned a Bachelor of Science in Mechanical Engineering from the Illinois Institute of Technology in 1992 and was commissioned through the Officer Candidates Course in 1997.
As a Combat Engineer platoon commander with the 1st Marine Division and 13th Marine Expeditionary Unit, Brigadier General Rosales conducted humanitarian operations in East Timor and security and recovery operations following the bombing of the USS Cole in Yemen. He was named the Marine Corps Engineer Officer of the Year in 2000.
Transitioning to the Reserve Component as a Captain, Brigadier General Rosales deployed twice in support of Operation IRAQI FREEDOM; first as a platoon commander in North Babil Province, and subsequently as a company commander in Anbar Province. During this period, he also conducted bilateral security cooperation exercises in Korea and Africa, and led a specialized counter-narcoterrorism training mission with the Mexican Marine Corps.
Selected for battalion command of 2nd Battalion, 24th Marines, he led a Joint Detachment to the Republic of Georgia under the Georgia Deployment Program and executed bilateral exercises with the Republic of Korea Marine Corps. Subsequent assignments included Regimental Executive Officer, 23rd Marines, and Director of Plans, MAGTF Staff Training Program.
In 2018, Brigadier General Rosales activated to the Pentagon as Deputy Chief of the Algorithmic Warfare Cross-Functional Team, known as “Project Maven”, where he oversaw the acceleration and integration of Artificial Intelligence and Machine Learning capabilities across the Department of Defense. He later served as a uniformed advisor to the Defense Innovation Unit's AI/ML team.
His most recent assignments include Commander, Special MAGTF-25 for UNITAS Brazil; Commander, Special MAGTF-23 for UNITAS Colombia; Marine Detachment Officer-in-Charge, Joint Enabling Capabilities Command (JECC), USTRANSCOM, deploying to both USEUCOM and USSOUTHCOM as Joint Planning Team lead for contingency and crisis planning. He has additionally served as Chief of Staff, Marine Corps Reserve Policy Board, and Deputy Chief of Staff, MARFORSOUTH. He relinquished his final O6 level command (JECC) in 2026.
Brigadier General Rosales' personal awards include the Defense Superior Service Medal, Legion of Merit, Bronze Star Medal, Defense Meritorious Service Medal, Meritorious Service Medal (third award), Navy Commendation Medal, Navy Achievement Medal, and the Combat Action Ribbon. He is married with two daughters.