Wash and prep all vegetables. Slice the pepper, onion, and mushrooms before you start cooking since everything moves fast.
Add the shaved steak and sliced vegetables to a large skillet over medium-low heat. Cook, turning the meat and vegetables every couple of minutes, until the steak is cooked through and the peppers are tender to your liking, about 15–20 minutes. Season with salt and pepper to taste.
While the steak cooks, make the queso. Add the Velveeta cubes and Rotel to a microwave-safe bowl. Microwave for 1 minute, remove and stir, then heat for an additional 1–2 minutes until completely melted and smooth. Stir well between each interval.
Slice the hoagie rolls and fill each with a generous portion of the steak and vegetable mixture.
Spoon the warm queso generously over the top of each sandwich. Serve immediately. Enjoy!