Remove any seeds from fruit slices, if necessary. Combine orange slices, apple slices, lemon slices and 4 rosemary sprigs in a large pitcher; gently muddle with a wooden spoon until the fruit releases juice, about 30 seconds. Stir in 3½ cups pomegranate juice and ½ cup orange juice. Refrigerate, uncovered, for at least 1 hour and up to 12 hours.
Just before serving, stir in 2 (12-ounce) cans seltzer. Serve in ice-filled glasses. Garnish with additional rosemary sprigs, if desired.
