Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9 inch springform pan.
In a large bowl, combine cake mix, root beer, eggs and oil. Beat for 2 minutes at medium speed. Pour into prepared pan.
Bake for 30 to 35 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from the pan to a wire rack to cool completely.
Spread softened ice cream over cooled cake. Freeze for several hours or overnight.