Place one turkey breast on a large cutting board and butterfly it open. Cover it with plastic wrap, then use a meat pounder or rolling pin to pound the turkey to an even 1/2-inch thickness. Remove the plastic wrap. Repeat this process with the second turkey breast. Butterflying and pounding ensures the turkey rolls up evenly and cooks uniformly.
Lay strips of bacon across the entire surface of each prepared turkey breast, trimming any excess bacon that overflows the edges. Evenly spread half the shredded cheddar cheese, 2 tablespoons of the chopped sage, 1 tablespoon of coarsely ground black pepper, and 1/2 teaspoon of crushed red pepper flakes over the bacon on each breast. Carefully roll each turkey breast up lengthwise into a tight cylinder. Secure each roll by tying it closed with butcher twine at 2-inch intervals. I find taking your time to roll tightly gives a beautiful spiral and helps the cheese stay inside.
Once the turkey rolls are tied, season the outside of each roll with the remaining black pepper and kosher salt to taste. This step adds flavor to the roasted exterior of the turkey rolls.
Light a chimney full of charcoal. When the charcoal is fully lit and covered with gray ash, pour it onto one side of the grill to set up two-zone (direct/indirect) cooking. Slice each turkey roll halfway between every piece of butcher twine, then place the sliced rolls, cut side down, on the hot side of the grill. Cook, flipping occasionally, until the turkey is well seared on each side and the internal temperature reaches 145-150°F. If the rolls aren’t done after searing, move them to the cool side of the grill, cover, and continue cooking until the proper temperature is reached. I like to use an instant-read thermometer to make sure the turkey is perfectly cooked and juicy.
Transfer the cooked turkey rolls to a cutting board and let them rest for 5 minutes to retain their juices. Remove the butcher twine, transfer the rolls to a platter, and serve immediately. Resting is key for juicy, tender slices.