The airplane was in cruise flight at 12,500 feet. The pilot told his wife that he was disengaging the autopilot to maneuver over the mountains. He then pressed the trim-disengage button on the control yoke. Shortly after, the airplane began rolling uncontrollably to the left and right. The pilot steadied the airplane with the rudder. He then began a 1/2 standard rate left turn. When he went to roll the airplane right, he said that the flight controls were difficult to manipulate. He attempted additional turns and found the problem continued. The pilot changed airspeed and found the problem increased with reduced airspeed. After that, he declared an emergency with air traffic control, began a descent, and proceeded to the nearest airport. The pilot said he was unable to locate the airport so he elected to perform a wheels up landing on a snow-covered field. During the landing, the airplane sustained substantial damage to the inboard left wing and the bottom left side of the forward fuselage. An examination of the airplane revealed no anomalies that could explain the stiff controls.