Preheat the oven to 375°. Line a sheet pan with a piece of parchment paper and place an oven-safe wire rack over the parchment paper. Set aside.
In a large skillet, heat the olive oil over medium high heat. Add the pancetta and cook until it has rendered some fat and started to crisp. Use a slotted spoon to transfer the pancetta to a small bowl. Add the onions, celery and apples to the pan and cook, stirring occasionally, until the vegetables and apple become slightly translucent and tender, stir in the sage, rosemary and pepper and cook for an additional minute until fragrant. Remove from heat and add the breadcrumbs and pancetta and toss to coat. Drizzle 1/2 cup of broth over the bread and stir well to mix. If the bread still seems dry. Add more broth 1-2 tablespoons at a time. Bread should be moist, but not soaked and still hold its shape. Sprinkle on the parmesan cheese and toss to combine.
Lay a piece of parchment paper on a flat, solid surface and one at a time, place one tenderloin in the center. Place another piece of parchment on top of the tenderloin and use the flat side of a meat mallet to pound the tenderloin down to about 1/4-1/3" thick, flipping halfway through pounding. Be careful not to tear the flesh. Set aside and continue with the second tenderloin. Set aside. Lay 3 slices of prosciutto lengthwise, side by side and slightly overlapping. Lay one tenderloin on top of the prosciutto horizontal to the direction of the prosciutto. Fill the center of the tenderloin with stuffing and carefully roll the prosciutto and turkey around the stuffing, like a jelly roll. Use kitchen string to secure the roll in in the middle and at each end. Place the turkey rolls on the wire rack and roast for 30-35 minutes or until turkey is cooked to 160°.
If there is leftover stuffing, spray an ovenproof ramekin with vegetable spray and put the rest of the stuffing in the dish. Dot with 1 teaspoon butter, cut into very small pieces and bake for 10-15 minutes with the turkey.
While turkey is cooking, make the gravy. Melt the butter in a small saucepan over medium high heat and add the sage leaf, cook for about a minute, then add the flour and whisk, cooking for about a minute. Add the wine, whisking constantly and cook for 30-45 seconds then whisk in the chicken broth -- continue stirring and cooking until mixture comes to a boil. Reduce heat to a light bubble and continue to cook for one minute. Add the cream and maple syrup and gravy master (if desired for color). Remove from heat and season with salt and pepper to taste.
Remove from oven and let the turkey rest for five minutes before carving. Slice the turkey roll in one inch wide slices. Serve with gravy and extra stuffing.