Line a loaf pan with plastic wrap. Place half of the walnuts in the bottom of the pan. Set aside. Combine the cream cheese and the Roquefort cheese in a food processor. Process until the mixture is smooth and creamy. Slowly add in the softened butter and process until it is incorporated and the mixture is smooth. Add salt and pepper to taste and pulse once or twice to blend.
Spoon half of the mixture over the walnuts in the pan, smoothing with a rubber spatula. Spread the remaining walnuts over the cheese layer, then top with the remaining cheese mixture, smoothing the top with a rubber spatula.
Cover with plastic wrap and refrigerate for several hours. To serve, unmold the loaf on a serving platter. Combine the apple slices and the lemon juices and toss to coat evenly. Arrange them around the cheese loaf and serve with whole-wheat crackers.
Makes about 30 to 40 appetizer servings