Preheat oven to 425°. In a large bowl, mix the first 9 ingredients. Place 1 sheet of phyllo dough on a work surface; brush with butter. Layer with 2 additional phyllo sheets, brushing each layer. (Keep remaining phyllo covered with a damp towel to prevent it from drying out.), Arrange 3/4 cup spinach mixture in a narrow row along the long end of phyllo to within 1 in. of edges. Fold bottom edge of phyllo over filling, then roll up. Brush end of phyllo dough with butter and press to seal. Repeat 4 times with phyllo sheets, butter and the spinach mixture. Place rolls on a parchment-lined 15x10x1-in. baking pan, seam side down., Cut rolls diagonally into 2-in. pieces (do not separate). Brush tops with remaining butter. Bake until golden brown, 12-15 minutes. If desired, serve with tzatziki sauce, lemon wedges and dill sprigs.