Put the contents of the salad kit in a medium bowl and toss to coat with the dressing; set aside.
Heat the vegetable oil in a large cast-iron skillet over medium-high heat. Combine 1 1/2 teaspoons black pepper and the red pepper flakes in a small bowl. Season the steaks with salt on both sides and sprinkle with the pepper mixture, pressing to adhere. Add the steaks to the skillet and cook 2 to 3 minutes per side for medium rare. Remove to a cutting board and let rest 5 minutes, then thinly slice against the grain.
Divide the steak between the rolls and top with the red onion, tomato and salad mixture.
Many bacon and blue cheese salad kits contain hardy greens (like kale) that need to soften a bit. Dress the salad and let it sit for about 10 minutes before assembling the sandwiches.