The private pilot was on a personal cross-country flight in a ski-equipped airplane, operating under Title 14, CFR Part 91, when the accident occurred. In a written statement, the pilot reported that he was flying about 75 feet above the ground looking for a landing area on a frozen river. He said the wind was gusting, the airplane rolled 90 degrees, and he was unable to counter the roll before the airplane impacted terrain. He reported there were no mechanical problems with the airplane prior to the accident.