In large bowl, mix 2 tablespoons of the butter and 1/2 teaspoon of the Cajun seasoning. Add potatoes; toss to coat. Place potatoes skin sides down in single layer on pan. Roast 18 to 22 minutes or until very tender when pierced with knife. Remove from oven; stir. Add sausage to potatoes, and move to one side of pan, making room for shrimp and corn.