In a food processor, add the porcini mushrooms, peppercorns, red pepper, granulated garlic, Italian seasoning and sugar and process until uniform and slightly fine. Add the salt and pulse twice until incorporated.
Rub the entire roast with the porcini rub, wrap in plastic and let it sit in the fridge overnight.
Preheat the oven to 225 degrees F. Position a wire rack over a baking sheet.
Heat a large skillet over medium-high heat. Add the oil and sear each side of the roast until browned, about 3 minutes a side. Transfer the roast to the prepared baking sheet and roast until an instant-read thermometer inserted in the center registers 115 to 125 degrees F (depending on desired doneness), 1 hour 15 minutes to 1 hour 45 minutes. Shut off the oven and leave the roast in there until it registers 130 to 140 degrees F, another 30 to 45 minutes. Let rest for 15 minutes.
Thinly slice the roast and serve with any collected juices.