In a large bowl, whisk the eggs until light yellow and frothy. Add the water, oil, cake mix, sour cream, and stir until combined.
3. Step
Separate the batter into three bowls. Add the cocoa powder to one of the bowls of batter, and stir until combined. Pour the chocolate batter into a piping bag, cut off the tip off of the piping bag.
4. Step
Add the strawberry gelatin powder to one of the bowls of batter, and stir until combined. Pour the strawberry batter into a piping bag, cut off the tip off of the piping bag.
5. Step
Pour the rest of the vanilla batter into a piping bag, cut off the tip off of the piping bag.
6. Step
Pipe the strawberry onto a parchment paper-lined baking sheet, starting in the upper left corner. Pipe 3 1-inch (2 cm) lines of batter diagonally across the pan, beginning with the strawberry, following with the chocolate, then the vanilla. Continue this pattern until you have filled the entire baking sheet. Tap pan on the counter 3 times to release any air bubbles.
7. Step
Bake for 7 minutes.
8. Step
While warm, flip cake carefully onto a large dish towel. While still warm, roll with the towel tightly but carefully. Set aside to cool for at least 30 minutes.
9. Step
Unroll the cake carefully, and peel away the parchment paper.
10. Step
Spread the vanilla frosting evenly on the cake.
11. Step
Gently roll the cake up making sure not to roll too tight or the frosting will come out of the sides of the cake roll.
