In a large mixing bowl, beat eggs; gradually beat in sugar. Add squash and mix well. Combine the flour, baking soda and cinnamon; add to squash mixture and mix well.
Line a 15 x 10 x 1 inch baking pan with waxed paper; grease and flour the paper. Spread batter evenly into pan. Sprinkle with walnuts. Bake at 375 for 13-15 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack for 10 minutes.
Turn cake onto a kitchen towel dusted with confectioners' sugar. Gently peel off waxed paper. Roll up cake in the towel, jelly-roll style, starting with a short side. Cool completely on wire rack.
In a small mixing bowl, beat cream cheese, butter, confectioners' sugar and vanilla until smooth. Unroll cake; spread filling evenly over cake within 1 inch of edges. Roll up again. Cover and refrigerate for 1 hour. Just before serving, dust with confectioners' sugar if desired.