For the sage butter: Combine all the ingredients into a medium bowl and mix with a fork until well blended. Sage butter can be made 2 days in advance, just make sure to let it come to room temperature before using.
For the turkey: Preheat the oven to 325 degrees F for convection ovens and 350 degrees F for conventional ovens. Place the oven rack in the lower portion of the oven.
Place the turkey in a roasting pan fitted with a rack. Sprinkle the inside of the turkey with salt and pepper and spread with one-third of the sage butter. Stuff with the chopped vegetables, lemon and bay leaves. Take one-third of the remaining butter and spread it under the skin on top of the breast. Spread the remaining butter all over the outside of the turkey. Tuck the wing tips underneath the bottom of the turkey. Using about a 12-inch piece of butcher's twine, tie the legs of the turkey together. Roast for 2 1/2 to 3 hours for convection oven or 3 to 3 1/2 hours for conventional oven, or until a thermometer inserted into the thickest part of the thigh reads 170 degrees F. Make sure to baste the turkey every 25 minutes or so. Do not baste for the last 30 minutes of roasting to allow the skin to crisp up. Allow the turkey to rest for 20 to 25 minutes before carving.