Split Rock Lodge and Cottages, one of the Pocono Mountains' best known resort and vacation communities, has been purchased by a group of regional residents - most of them Split Rock property owners - from Restaurant Associates Industries Inc., New York. The new owner took over today as Pocono Recreation Inc. The purchase price was $840,000. The purchasing group is headed by John Bari, president of Forest Glen, a vacation home community near Blakeslee.