Roast the long hots. Toss long hots peppers in a light coat of oil (about 1 tablespoon) and a pinch of salt. Roast over medium-high heat — on a grill, under a broiler, or on a high-heat appliance — turning occasionally until skins are blistered and flesh is tender, about 8-10 minutes. Then cover with foil and let steam 5 minutes. Dice half of the long hots for mixing into the meat; leave the rest whole for topping. Remove seeds and pith to reduce heat if desired.
Heat the griddle or skillet. Heat your griddle or a large skillet over low heat. *Low heat on the griddle is the key to moist, tender shaved beef. High heat will dry it out quickly.
Cook the onions. Add 2 tablespoons of butter to the griddle or skillet. Add diced onions to the butter. Season with salt and pepper. Cook on low, stirring occasionally, until soft and translucent, about 8–10 minutes.
Cook the shaved ribeye. When the onions are almost done cooking, add shaved ribeye to the griddle in a separate area. Keep the heat on low and gently separate the beef as it cooks. Once nearly cooked through (2–3 minutes), season with salt and plenty of freshly cracked black pepper. Mix the onions and the diced long hots into the beef.
Add the cheese. Spread the meat and onion mixture out a bit on the griddle, and lay the Cooper Sharp American cheese slices over the top. Allow the cheese to begin to melt, about 1-2 minutes, and then mix it into the beef using a folding motion.
Steam the bread. Divide the cheesesteak mixture into two equal piles, and use your spatula to shape the meat into a rough shape that matches the size of your hoagie rolls. Place the hoagie rolls cut-side down over the cheesesteak piles and let steam for about 2 minutes to soften the bread and finish melting the cheese.
Build the sandwich. Scoop the meat and cheese into the rolls. Top with the reserved whole roasted long hots. Serve immediately. *You can also wrap the cheesesteaks in deli-style paper to rest for 2-3 minutes. This helps to further soften the rolls and steam the sandwich.