Season roast with salt, pepper and garlic powder.
Heat oil in a large skillet/pan over medium-high heat. Sear roast on all sides until browned; transfer to a plate. Sauté the onions until soft, scraping up any browned bits leftover from the roast. Add the garlic and sauté until fragrant (about 30 seconds).
Place the roast in the bowl of a 6-quart (litre) slow cooker. Add the cooked onions, soup, consommé, stock and Worcestershire sauce. Cook on low for 6-8 hours or high for 3-4 hours until meat is fork-tender.
In the last 10 minutes of cooking time, preheat oven to 350°F (180°C). Arrange rolls on a large baking sheet.
Remove roast, let rest for 10 minutes, then slice (or shred with forks). Strain the au jus (liquid) leftover in the slow cooker into a jug.
Spread hoagies with butter; stuff the meat and cheese slices into the rolls. Toast the sandwiches in preheated oven for 5 minutes or until the cheese just begins to melt.
Serve with small bowls of au jus for dipping.