Heat a large Dutch oven over medium-high heat. Rub roast with vegetable oil and season liberally with salt and pepper or Montreal Seasoning. Brown in the hot pan on all sides, 10-12 minutes. Remove from heat.
Bring brine and flavor pouch to a boil in a saucepot or large Dutch oven I secure mine with kitchen twine to side of pot. Turn heat off and let cool. Combine brine and meat in the pot or in another container and refrigerate 3 days, turning meat occasionally.
To cook, bring meat to room temperature. Sprinkle sugar into the pot and combine with sauce. Preheat oven to 325F and roast about 3 1/3-4 hours. Meat may also be cooked in a slow cooker on high for 4 hours or low for 7 hours.
Remove roast to a carving board and cover with foil. Let rest 30 minutes. Strain or finely grind sauce in a food mill and return to pot. Whisk in tomato paste and ground ginger snaps if snaps do not dissolve completely pass through food mill or sieve again. Adjust black pepper in sauce to taste.
To serve, thinly slice meat and serve with wilted or sauted dark greens and mashed potatoes with sour cream or potato cakes alongside.