The 34-year-old Randall joins the Astros from the Pirates, where he spent the past three years as the club's Major League rehab coordinator, physical therapist and assistant athletic trainer. He also spent the 2012 season as Pittsburgh's Minor League rehab coordinator.
In addition to his time with the Pirates, Randall also had stints on the medical staffs with the Dodgers, Seattle Seahawks and the New England Patriots.
The 32-year-old Roberts spent the past five seasons as the Astros' Minor League rehab coordinator, running the organization's Minor League rehab programs and assisting with Major League rehab out of the Astros' Spring Training facility.
Barringer, 28, joins the Astros after spending the past five seasons as a Minor League athletic trainer with the Cubs and D-backs organizations.
Balkovec, 28, who will be based out of Kissimmee, Fla., spent three of the past four seasons in the Cardinals organization, serving as a Minor League strength and conditioning coordinator and as a Minor League strength and conditioning coach.
Quinn Roberts is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.