Preheat your Blackstone griddle to medium-high heat. While it is heating up, spread the softened butter on the insides of the split hoagie rolls.
Place the rolls butter-side down on the griddle to toast them until they are golden brown (about 1-2 minutes). Remove them and set aside.
Drizzle vegetable oil onto the griddle. Add the diced onions (and bell peppers, if using). Sauté them, tossing frequently, until they are soft and beautifully caramelized (about 4-5 minutes). Move them to a cooler side of the griddle.
Add a little more oil to the hot zone and drop the shaved ribeye onto the griddle. Season generously with salt and pepper.
As the meat cooks, use two sturdy metal spatulas to quickly chop and shred the meat directly on the flat top. Cook until no longer pink (about 3-4 minutes).
Bring the caramelized vegetables back into the center and mix them thoroughly with the cooked meat.
Divide the meat and vegetable mixture into 4 equal, rectangular piles (roughly the length of your hoagie rolls). Turn off the burners directly under the meat.
Place 2 slices of Provolone cheese over each pile. The residual heat from the griddle will perfectly melt the cheese within a minute.
Take a toasted hoagie roll and place it upside down right on top of a cheesy meat pile. Slide your large spatula completely under the meat and carefully flip the entire sandwich over. Serve immediately!