1. For filling, melt 1 tablespoon of the butter in a medium skillet over medium heat. Add the onion and cook about 5 minutes or until softened. Add the spinach and cook, stirring constantly, for 2 to 3 minutes or until moisture is evaporated. Remove from heat and stir in ricotta, feta, egg, salt, nutmeg, and pepper. Set aside.
2. Preheat oven to 375 degree F. Grease a cookie sheet. Melt the remaining 7 tablespoons of butter in a small skillet. Place 1 phyllo sheet lengthwise on a sheet of wax paper or clean towel. (Keep remaining phyllo covered with a damp towel.) Brush lightly with melted butter and sprinkle with 1 tablespoon bread crumbs. Repeat layering and buttering 2 more phyllo sheets, then spread a third of the filling along 1 long edge of phyllo.
3. Using wax paper as a guide, roll phyllo from long edge jelly-roll fashion. Place phyllo roll seam-side down on prepared cookie sheet and press ends to seal. Brush the top with butter. With a sharp knife, cut slices about halfway through phyllo roll at 1-inch intervals. Repeat process 2 more times with remaining phyllo, butter, bread crumbs, and filling to make 2 more rolls.
4. Bake rolls about 20 minutes or until golden brown. (If frozen, bake an additional 15 to 20 minutes.) While still warm, cut rolls into slices. Makes about 45 appetizers.