The airplane was substantially damaged during an in-flight recovery after the captain attempted an intentional aileron roll maneuver during cruise flight and lost control. The cargo flight was being operated at night under the provisions of 14 CFR Part 135 at the time of the accident. The captain reported the airplane was "functioning normally" prior to the intentional aileron roll maneuver. The captain stated that the "intentional roll maneuver got out of control" while descending through flight level 200. The captain reported that the airplane "over sped" and experienced "excessive G-loads" during the subsequent recovery. The copilot reported that the roll maneuver initiated by the captain resulted in a "nose-down unusual attitude" and a "high speed dive." Inspection of the airplane showed substantial damage to the left wing and elevator assembly.