Heat oven to 375°F (350°F for dark or nonstick pan). Line bottom only of 15x10x1-inch pan with foil or waxed paper; spray with baking spray with flour. Place paper baking cup in each of 8 regular-size muffin cups.
In large bowl, beat eggs with electric mixer on high speed about 5 minutes or until thick and lemon colored. Add cake mix, water and oil; beat on low speed 30 seconds, then on medium speed 1 minute, scraping bowl occasionally. Pour 3 1/2 cups batter into pan. Divide remaining batter among muffin cups.
Bake 14 to 16 minutes or until cake springs back when lightly touched in center and cupcakes test done when toothpick inserted in center comes out clean. If necessary, run knife around edges of pan to loosen cake. Turn cake upside down onto clean kitchen towel sprinkled with 1 tablespoon powdered sugar; carefully remove foil. While hot, carefully roll up cake and towel from narrow end. Cool completely on cooling rack, about 1 hour. Cool cupcakes 10 minutes. Remove from pan; cool completely, about 30 minutes. Save cupcakes for another use.
Meanwhile, in medium microwavable bowl, microwave whipping cream uncovered on High 1 minute to 1 minute 30 seconds or until it just starts to boil. Stir in chocolate chips and corn syrup; let stand 3 minutes. Beat gently with wire whisk until smooth. Beat in vanilla. Refrigerate about 1 hour, stirring every 15 minutes, until spreading consistency.
Unroll cake carefully, and remove towel. Spread filling evenly over cake; roll up cake. Place cooling rack on sheet of waxed paper. Place cake roll on cooling rack; frost cake. Using fork, drag tines through frosting to look like log. Let stand 15 minutes. Transfer cake to serving platter. Store loosely covered in refrigerator. Let stand at room temperature 30 minutes before serving.