Coat 15x10x1-inch baking pan with nonstick cooking spray. Line pan with waxed paper. Coat waxed paper with nonstick cooking spray; lightly flour. Set aside. In medium bowl, combine flour, cinnamon, soda, baking powder, ginger, cloves, and salt; set aside.
In medium bowl, beat egg yolks with electric mixer on high speed for 5 minutes or until thick and lemon colored. Beat in molasses, melted butter, and the 1 teaspoon vanilla just until combined.
Thoroughly wash beaters. In another bowl, beat egg whites on medium speed until soft peaks form (tips curl). Gradually add granulated sugar, beating until stiff peaks form (tips stand straight). Fold egg yolk mixture into egg whites. Sprinkle flour mixture over egg mixture; fold in gently just until combined. Fold in sweet potato. Spread batter evenly in prepared pan.
Bake in a 350 degree F oven about 10 minutes or until cake springs back when lightly touched. Immediately loosen edges of cake from pan and turn out onto a towel sprinkled with powdered sugar. Carefully remove waxed paper from cake. Starting from one of cake's short sides, roll up towel and cake into a spiral. Cool on wire rack. Unroll cake.
In chilled medium bowl, combine whipping cream, the 1/3 cup sifted powdered sugar, 1 teaspoon ground cinnamon, 1 teaspoon vanilla, and 1/8 teaspoon ground cloves. Beat with chilled beaters of an electric mixer on medium speed until soft peaks form.
Spread cake with half of the whipped cream, spreading to within 1 inch of edges. Roll up cake without towel. Spread remaining whipped cream mixture evenly over outside of cake. Garnish with pecan halves. Chill in the refrigerator for up to 2 hours. Makes 10 servings.