Preheat your oven to 325°F (165°C).
Season the chuck roast generously with salt and pepper.
Heat olive oil in a large skillet over medium-high heat.
Sear the beef on all sides until browned, about 4-5 minutes per side.
Transfer the seared beef to a large Dutch oven.
Add sliced onions and minced garlic to the skillet.
Pour in beef broth and Worcestershire sauce.
Sprinkle in Italian seasoning and red pepper flakes.
Bring the mixture to a gentle simmer, then cover the Dutch oven and transfer to the oven.
Cook for approximately 3-4 hours, or until the beef is fork-tender.
Remove the beef from the pot and shred it using two forks.
Strain and reserve the remaining broth.
Slice the Italian rolls in half and toast them lightly if desired.
Assemble the sandwiches by layering the shredded beef on the rolls.
Top with sliced peppers and giardiniera.
Drizzle with reserved broth before serving.