How to Make It
Take the roast out of the refrigerator and let it come to room temperature about 45 minutes before roasting.
Heat oven to 325º F. Place the roast on a metal rack in a roasting pan, fat-side up, and rub with the chili and salt. Toss the sweet potatoes with the olive oil and place around the roast.
Cook until an instant-read thermometer inserted in the center registers at least 120º F (for rare), about 1 hour and 15 minutes (15 to 20 minutes per pound). The potatoes should be fork-tender. Remove from oven.
Loosely cover the roast with foil and let stand 10 to 15 minutes. (The temperature will rise to 125º F.) Slice half the roast. Serve with the sweet potatoes. Wrap and refrigerate the remaining meat for another meal.