Three days before serving, in a blender or spice grinder, finely grind salt, marjoram, thyme, juniper berries, peppercorns, and anise seeds.
Remove and discard leg truss from turkey. Pull off and discard any lumps of fat. Remove giblets and neck; save neck for gravy. Rinse turkey inside and out; pat dry. Cut off wing tips to the first joint and reserve for gravy. Rub half the herb mixture all over turkey; sprinkle remaining in body cavity. Cover and chill for 3 days.
Preheat oven to 325° (convection not recommended). Put rosemary sprigs and garlic inside turkey body cavity. Gently push your hand between skin and turkey breast to separate skin from breast. Spread about half the butter over breast under skin. Melt remaining butter and brush lightly over top of turkey. Coat a V-shaped rack with cooking-oil spray and set in a 12- by 17-inch roasting pan. Place turkey, breast down, on the rack. Roast turkey for 1 3/4 hours.
Meanwhile, cook turkey wing tips and neck for pan gravy. Remove turkey from oven and turn breast side up. Return to oven. Roast until a meat thermometer inserted straight down through thickest part of breast to the bone registers 160°, 45 to 60 minutes longer.
Tip turkey to drain juices from cavity into pan and transfer to a platter. Let stand in a warm place, uncovered, for 15 to 30 minutes. Finish gravy, then carve turkey.
Note: In nutritional analysis, sodium is N/A.