Remove giblets and neck from turkey. Reserve giblets for Lemon-Parmesan Stuffing. Reserve neck for another use. Rinse turkey thoroughly with cold water; pat dry.
Combine butter and lemon juice; stir well with a wire whisk. Carefully loosen skin from turkey at neck area, working down to breast and thigh area. Rub two-thirds of lemon butter mixture under skin.
Place 8 to 10 sage leaves between skin and meat. Rub inside of body and neck cavities with lemon halves.
Sprinkle cavities evenly with 1/2 teaspoon salt and 1/4 teaspoon pepper.
Lightly stuff Lemon-Parmesan Stuffing into body and neck cavities of turkey.
Place turkey on a lightly greased rack in a roasting pan, breast side up. Tie legs together with heavy string. Lift wingtips up and over back, and tuck under bird.
Coat turkey with remaining one-third lemon butter mixture; sprinkle with remaining 1/2 teaspoon salt and 1/4 teaspoon pepper.
Pour wine into pan. Insert a meat thermometer into meaty portion of thigh, making sure it does not touch bone.
Bake, uncovered, at 325 for 3 1/2 hours on bottom oven rack or until thermometer inserted into thickest part of leg registers 180 and center of stuffing reaches 16
Let turkey stand 15 minutes before carving.
While turkey stands, pour pan drippings through a wire-mesh strainer into a large saucepan, discarding solids.
Combine flour and 3/4 cup pan drippings, stirring until mixture is smooth; add to remaining pan drippings in saucepan, adding enough water to measure 2 1/4 cups, if necessary. Bring mixture to a boil, stirring constantly; reduce heat, and simmer, uncovered, 5 minutes or until mixture is thickened, stirring often.
