Heat oven to 375°F (350°F for dark or nonstick pan). Line bottom only of 15x10x1-inch pan with cooking parchment paper; spray with baking spray with flour. Place paper baking cup in each of 7 regular-size muffin cups.

In large bowl, beat eggs with electric mixer on high speed about 6 minutes or until thick and lemon colored. Add cake mix, water and oil; beat on low speed 30 seconds, then scrape bowl. Beat on medium speed 1 minute. Pour 3 cups of the batter into pan; spread evenly. Divide remaining batter among muffin cups.

Bake 10 to 12 minutes or until cake springs back when lightly touched in center. Bake cupcakes 13 to 15 minutes or until toothpick inserted in center comes out clean.

Meanwhile, sprinkle powdered sugar over clean kitchen towel. Run knife or metal spatula around edges of pan; carefully turn cake upside down onto kitchen towel. Peel away parchment paper. Immediately roll up cake and towel from narrow end. Cool completely on cooling rack, about 45 minutes, with seam centered on bottom of cake. Cool cupcakes 10 minutes. Remove from pan. Cool completely, about 30 minutes. Save cupcakes for another use.

Carefully unroll cake; allow the end to remain slightly curled. Spread filling evenly to within ½ inch of edge. Reroll filled cake, using kitchen towel to help roll up cake; remove towel. Place cake on serving platter, making sure seam is centered on bottom. Place strips of waxed paper around edges of platter.

Frost top and sides of cake with 1 cup frosting. Slowly pour sprinkles over top and sides of cake to cover. Cup your hand as you pour and press the sprinkles into sides of cake, using the waxed paper to catch extra sprinkles. Remove waxed paper after frosting and sprinkling. Refrigerate 30 minutes before slicing. Store loosely covered in refrigerator.