Preheat oven to 400°F. Heat 1 teaspoon of the oil in a large oven-proof skillet over medium-high. Add ground beef and 1 teaspoon of the salt, and cook, stirring occasionally, until browned and cooked through, 6 to 8 minutes. Transfer beef to a plate lined with paper towels. Discard drippings. Add the remaining oil, onion, bell pepper, and 1/2 teaspoon of the salt to the skillet, and cook over medium-high, stirring occasionally, until softened, 4 to 5 minutes. Add garlic and cook for about 30 seconds until fragrant. Mix in tomatoes, ketchup, mustard, relish, Worcestershire, chili powder, cooked beef, and remaining salt. Bring to a simmer and cook for 3 minutes. Remove from heat, top with Cheddar cheese, shingle dinner rolls on top, and brush with melted butter. Bake until rolls are warmed through and cheese is melted, about 10 minutes.