Prepare the turkey and add the butter to it. Remove the neck and insides of the turkey, and pat dry with paper towels. Use your hands to loosen the skin on the turkey breast and legs. Then rub all but about 2 tablespoons of the compound butter under the skin, being careful to leave it intact. Set the remaining butter aside.
Truss the turkey. Truss the turkey with butcher's twine. Trussing the turkey helps it stay juicier, and helps it hold its shape for a pretty presentation. Here's How to Truss a Turkey. Begin roasting. Place the turkey, breast side up, on the roasting rack and into the oven. After about 15 minutes, use a basting brush to spread the rest of the butter on the turkey's surface. Continue to roast until the skin is golden brown, about 10 more minutes. Then remove it from the oven and reduce the heat to 350°F.
Turn the turkey and add the bacon. Gently turn the turkey over so the breast side is down on the rack. (Yes, this is tricky with a big turkey -- you might want to use heat resistant gloves or hold each end with paper towels for a better grip.) Cover the back and sides of the turkey with the bacon strips, using rosemary sprigs to hold them in place if they're slipping.
Continue roasting. Return the turkey to the oven (as it is, breast side down) and roast until the internal temperature is 155°F. The final internal temperature will be about 165°F, as the turkey will continue to cook for several minutes outside the oven. The juices should run clear and the legs should move easily when it's done. Cooking times might vary, but it should take about 2 hours. If your turkey is getting too brown before it has finished cooking, cover it loosely with foil.
Rest the turkey, carve and serve. Wait at least 20 minutes before carving (this allows the juices to settle). Remove the bacon and add it to your serving platter. Place the turkey slices over the bacon as you carve. Garnish your platter with fresh herbs.