Place a large skillet over medium-high heat. Add oil.
Liberally season both sides of the roast with salt and pepper. Sear the roast in hot oil for 2-3 minuter per side until a nice crust forms. Transfer to your slow cooker.
To the slow cooker add beef consommé, french onion soup, beer, onion, and garlic powder. Move everything around a bit to mix the liquids and seasoning together.
Cover and cook on LOW for 8 hours or HIGH for 4 1/2 hours.
Remove lid and take out the roast. Place on a cutting board. Use a slotted spoon to remove the onions; place in a bowl. Strain the cooking liquid into a fat separator (or a bowl) and let sit. Rough chop or shred the roast. Pour the fat off the cooking liquid (or skim off fat if in a bowl) and transfer to small bowls for serving.
Assemble sandwiches by dividing the meat among the rolls. Top with a slice of cheese that's been cut in half and lay over the top to cover the whole sandwich. Top with cooked onions if desired. Serve immediately with au jus (strained cooking liquid).
If you want to leave out the beer, add 1 more can of beef consommé instead.
Sometimes we like to toast our rolls before and it's delicious! It adds another layer of flavor and texture. It also helps the bread stay together with all that au jus.