Step 1 In a large, heavy-bottom saucepan, briefly cook the frozen spinach in a little boiling water, stirring just until thawed. Remove from heat and drain the spinach well, discarding the water. Return the spinach to the pan.
Step 2 Stir in the mozzarella and Romano cheeses, along with the one-quarter cup butter to form the filling. Season to one-eighth teaspoon salt and a small pinch each pepper and cinnamon, or to taste. Mix the filling well; the warmth from the pan and spinach will melt the other ingredients slightly. This makes 3 cups filling.
Step 3Working quickly, brush 2 sheets phyllo with a light coating of melted butter, and place 1 sheet on top of the other. Place one-third cup filling along the length of the sheets, leaving 2 inches at either end. Turn in the ends and roll the filling into the sheets, as with a burrito; continue folding until a long roll is formed. Brush the roll lightly with melted butter and place on a baking sheet. Continue until all of the filling is used, spacing the rolls about 2 inches apart. This makes 6 rolls.
Step 4Bake the rolls until golden brown, about 20 to 25 minutes, rotating halfway for even coloring. Cool slightly, then cut each roll diagonally into 2-inch pieces. Serve warm.