For the 5-alarm dry brine: Mix together the salt, sugar, pepper, sage, chile powder, fennel seed, garlic powder, onion powder and red pepper flakes. If not using right away, store in an airtight container for up to 2 months.
For the turkey: Measure out 1 tablespoon of the 5-Alarm Dry Brine per 5 pounds of turkey (a 12-pound turkey will take 2 1/2 tablespoons). Rub the measured brine all over the exterior of the turkey. Add an additional tablespoon of the brine to the inside of the bird, rubbing it on the underside of the breast.
Let the turkey sit at room temperature for 30 minutes, then pat the turkey dry with paper towels.
Preheat the oven to 375 degrees F.
Place one strip of bacon down the center of the turkey breast, making sure that at least 1 inch of the bacon hangs over the breast on both the neck and cavity side. Continue to layer the bacon vertically along the breast of the turkey with a slight overlap, making sure to maintain the overhang on both ends. The bacon on the far edges of the breast may not reach the end of the cavity, so tuck those pieces in the crease between the thigh and the body.
Gather all of the bacon ends on the neck side and pierce the ends through with a single sprig of rosemary. Use the same rosemary to pin the bacon to the breast near the wishbone. On the cavity side use 1 onion cut into quarters to secure the bacon against the back side of the breast.
Arrange the carrots, celery and remaining sprigs rosemary in a roasting pan and rest a rack on top. Carefully transfer the turkey to the rack.
Roast the turkey until an instant-read thermometer inserted into the thickest part of the thigh (avoid touching bone) registers 160 degrees F, 1 hour 30 minutes to 2 hours. (Upon resting, the temperature should raise to a minimum of 165 degrees F.) If the turkey is browning too quickly, reduce the oven temperature to 350 degrees F and tent the pan with aluminum foil. Let the turkey rest for 30 minutes before carving.