Line a 15 x 10 x 1 inch jelly roll pan with aluminum foil and spray generously with non stick cooking spray.
In a mixing bowl beat eggs for 5 minutes until thick. Gradually beat in sugar. On low speed add in water and vanilla. Add in flour, baking powder, salt, and cocoa and beat together just until smooth. Pour into the prepared jelly roll pan. Bake at 375 degrees for 13-15 minutes.
When done cooking and while cake is still hot, invert cake onto a flour sack dish towel (or a thin towel) that is generously sprinkled with powdered sugar. Carefully spread the powdered sugar around with your fingertips. Be sure to sprinkle the powdered sugar on generously!
Carefully remove the foil from the back of the cake after you get it on the dish towel.Roll cake and towel up together from the narrow end and leave the seam side down and let it cool completely on the counter all wrapped up. While the cake is cooling prepare the filling.
Beat together the heavy whipping cream and powdered sugar on medium/high speed until it is very thick. Then add in the diced strawberries. Stir them in by hand until all are coated. When the cake is cool, carefully unroll the cake. Spread the prepared filling all over the cake (even to the edges) and then roll the cake roll back up very gently. (Don't roll the towel this time.) Some of the filling may spill out the side a little bit. Place on a serving plate and then cover with chocolate frosting.
To make the frosting, using a hand mixer beat together the butter, powdered sugar, cocoa, vanilla, and milk until smooth. If it's too thick add a little more milk. If it's too runny add a little more powdered sugar. You'll want it to be spreading consistency to cover the cake roll.
Right before serving top with whipped topping and sliced strawberries. Slice the cake roll and serve.