Sprinkle main cavity generously with salt and pepper. Place 4 tablespoons plain butter and all fresh herb sprigs in main cavity. Tuck wing tips under. Tie legs together loosely. Rub remaining herb butter over outside of turkey. Sprinkle turkey generously with salt and pepper. Place turkey in oven and roast 20 minutes. Reduce oven temperature to 350F. Roast turkey 30 minutes; pour 1 cup broth over and add 1 tablespoon plain butter to roasting pan. Roast turkey 30 minutes; baste with pan juices, then pour 1 cup broth over and add 1 tablespoon butter to pan. Cover turkey loosely with foil. Roast turkey until thermometer inserted into thickest part of thigh registers 175F, basting with pan juices and adding 1 cup broth and 1 tablespoon butter to pan every 45 minutes, about 1 hour 45 minutes longer. Transfer turkey to platter; let stand 30 minutes (internal temperature will rise 5 to 10 degrees).