Prepare the beef: Slice the beef into thin strips. If it's difficult to slice, freeze the beef for about 30 minutes beforehand to firm it up.
Layer the slow cooker: Add the sliced beef, green and red bell peppers, onion, garlic, beef broth, Worcestershire sauce, garlic powder, onion powder, paprika, salt, and black pepper into the slow cooker. Stir everything to combine.
Cook the beef: Cover and cook on low for 6-8 hours or high for 3-4 hours, until the beef is tender and the flavors are well combined.
Prepare the sandwiches: Preheat your oven's broiler. Split the hoagie rolls and place them on a baking sheet. Use a slotted spoon to fill each roll with the cooked beef and vegetable mixture.
Add the cheese: Top each sandwich with a slice of provolone cheese. Place the sandwiches under the broiler for 1-2 minutes, just until the cheese is melted and bubbly.
Serve: Remove from the oven and serve immediately.