Preheat oven to 350°. Line a jelly roll (15x10x1-inch) pan with foil and spray with baking spray that has flour in it.
Beat eggs in a large bowl on high speed for about 5 minutes, or until they are thick and lemon colored. Add cake mix, water, and oil. Beat on low speed for 30 seconds and then medium speed for 1 minute, scraping the sides of the bowl occasionally. Pour into pan.
Bake 11-14 minutes, or until cake springs back when lightly touched. Do not overbake - mine cooked in about 11 minutes. Remove from oven and run a knife around the edges of the pan if the foil did not cover the whole thing to make sure the cake does not stick.
Lay a clean kitchen towel on a flat surface. Sprinkle with the powdered sugar. Turn the hot cake upside down on the towel and remove the foil. While hot, roll up the cake in the towel, starting at the short end. Cool completely on a cooling rack, while rolled up, about 1 hour.
Make the buttercream: Cream butter and caramel sauce until butter is broken up and chunky, then add powdered sugar and vanilla and mix until smooth and fluffy.
Make the ganache: Add the heavy cream and chocolate chips to a microwave safe bowl or measuring cup. Heat for 1 minute, then whisk until smooth, heating additional 30 seconds if needed to get the chocolate chips to melt.
Once cake is cooled, unroll the cake carefully. Spread the caramel buttercream evenly over the cake. Reroll the cake. It should roll easily.
Place the cake on a cooling rack with a cookie sheet underneath to catch any drips. Drizzle the cake with the ganache. Top with toasted pecans.
Store loosely covered in the refrigerator for up to 3 days.