Whisk together curing mixture, brown sugar, pepper, paprika, bay leaf, allspice, and garlic powder in a bowl. Rub mixture over venison roast, and wrap tightly in plastic wrap. Place roast in a bowl; refrigerate for 5 days.

Remove roast from the refrigerator and rinse thoroughly to remove the curing mixture. Place in a bowl with water to cover, and soak, refrigerated, for 2 hours. Drain.

Preheat oven to 250 degrees F (120 degrees C).

Season roast with additional black pepper and brown sugar, and place in a roasting pan.

Bake, uncovered, in the preheated oven until a meat thermometer inserted near the center reads 160 degrees F (70 degrees C), about 2 hours.