Line 15x10x1-inch pan with parchment; spray lightly with cooking spray.
Separate 1 egg. Reserve yolk for later use. Microwave 3 Tbsp. butter in microwaveable bowl on HIGH 25 sec. or until melted. Add 1/3 cup powdered sugar, 1/4 cup flour and egg white; whisk until blended.
Divide mixture between three small bowls; using a toothpick tint to desired colored. Spoon into 3 small resealable plastic bags. Cut small piece off one bottom corner of each bag; use to pipe nickel size dots 1" apart in a random pattern onto parchment-lined pan. Freeze 30 min. or until firm.
Heat oven to 350°F. Separate remaining eggs, placing egg whites in medium bowl, and yolks in large bowl along with the reserved egg yolk. Beat egg whites with mixer on high speed until soft peaks form. Gradually add 1/4 cup granulated sugar, beating constantly until stiff peaks form. Set aside.
Melt 1/4 cup (4 Tbsp.) of the remaining butter. Beat egg yolks and 1/4 cup of the remaining granulated sugar in large bowl with mixer on medium speed 10 min. or until thick and lemon colored. Add melted butter, 1/4 cup water and remaining flour; mix well. Gently stir in beaten egg white mixture until blended.
Remove prepared pan from freezer. Gently spoon cake batter over colored dots on prepared pan; spread batter to evenly cover dots and bottom of pan. Gently tap pan on counter 2 or 3 times to remove any air bubbles.
Bake 10 to 12 min. or just until top of cake springs back when touched in center. (Do not overbake or the cake will crack and be difficult to roll up.)
Remove cake from oven; top with additional parchment sheet and large baking sheet or cutting board. Carefully flip cake and pans over, then remove baking sheet. Peel parchment off cake. (Cake should be dots-side up.) Cool cake completely.
Place additional sheet of parchment over cake; gently flip cake over again so cake is dot side down on work surface. Microwave remaining granulated sugar and water in microwaveable bowl 1 min.; stir until sugar is dissolved. Brush over cake.
Beat cream cheese and remaining butter in large bowl with mixer until blended. Add remaining powdered sugar; mix well. Gently stir in COOL WHIP; spread onto cake, leaving 1-inch border around all sides of cake.
Top COOL WHIP with sprinkles. Starting at one long side, roll up cake tightly, using parchment to help roll the cake and removing parchment as cake is rolled. Wrap cake with parchment; twist parchment at both ends of cake to secure roll. Place on baking sheet. Refrigerate 2 hours.
Unwrap cake, then cut into slices just before serving.