Brown roast on all sides in shortening in a Dutch oven. Cover roast with water. Combine next 13 ingredients (vegetables and spices); pour over roast. Cover and simmer 2 hours or until meat is tender. Remove roast; cool 10 minutes. Slice and arrange attractively on a deep serving platter; garnish with lemon slices. Set aside.
Line large strainer with cheesecloth; strain pan liquid, reserving 2 cups liquid. Discard vegetables and spices. Pour reserved liquid into a medium saucepan; add egg whites. Simmer (do not boil) 10 minutes. Line strainer with cheesecloth; strain liquid, and discard egg whites.
Soften gelatin in cold water 5 minutes; add reserved hot liquid, stirring until gelatin is dissolved. Pour gelatin mixture over sliced roast and lemon slices; chill until firm. Garnish with fresh parsley, if desired.