Put garlic powder, salt and pepper in a roaster pan. Place roast on top, then roll to coat the roast, sprinkling some on top. Roast, uncovered, for 1 hour.
Turn oven down to 350 degrees F.
Add 1 1/2 gallons water to pan and cover with foil.
Roast 3 hours. Let cool and thinly slice. Save liquid for au jus.
Slice hoagie buns open and toast them. Add 4 ounces meat to each bun bottom. Put the bun tops on. Pour 4 ounces au jus into each of 10 small bowls. Serve with sandwiches for dipping.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.