1 Place sliced lemon, or a whole onion into the cavity of a turkey while roasting, the flavor will create a tasty juice for gravy. 2  If you have chosen to use a roasting bag, open the bag for the final 15 to 20 minutes of roasting to allow the skin of the turkey to crisp.he oven-roasting bag keeps the turkey very moist and it speeds up the roasting time. The following cooking times can be used as a guideline for an unstuffed turkey roasted in an oven bag in a 350°F conventional oven. An additional 30 minutes or more may be required for a stuffed turkey.