Heat vegetable oil over medium-high heat in a large cast iron skillet. Using tongs, sear meat on all sides until browned and transfer to a 6 qt. (or larger) slow cooker. Add all remaining roast ingredients to slow cooker and give them a stir.
Cover and cook on low for 8-10 hours or on high for 4-6 hours OR until roast is super tender and easily sheds with a fork.
Once tender, shred roast and discard excess fat. Continue to cook on low for 30 minutes for the roast to absorb some of the juices.
Meanwhile, preheat oven to 400 degrees F. Split rolls and lay them cut side up on a large baking tray. Bake for 5 minutes to toast the buns.
Using tongs (or place meat in a colander over a bowl to drain juices), pile bottom side of buns with meat, followed by desired toppings (pepperoncini, roasted bell peppers, giardiniera etc.), followed by cheese. If using thinly sliced cheese, fold each slice in half and use two slices per hoagie. If using traditional slices, use one slice per hoagie. and cut each piece in half so it fits the shape of the bun.
Return baking tray to the oven (leaving both top and bottoms cut side up) and bake at 400 degrees F for 5-10 minutes or until cheese is completely melted. Serve immediately. You may serve the remaining liquid as a dip for the sandwiches, if desired.
