Preheat the oven to 350°F.

In a small bowl, mix together the sesame seeds, poppy seeds, dried onion flakes, black sesame seeds if using, and garlic salt. Store any extra topping in an airtight container.

In another small bowl, mix 2 tablespoons melted butter with 2 tablespoons of the everything bagel topping. Set aside.

In a medium skillet over medium-high heat, melt 2 tablespoons butter. Add the chopped bell pepper and onion. Cook until the vegetables are tender and lightly golden around the edges. Remove from the skillet and set aside.

In a large skillet over medium-high heat, add olive oil and shaved roast beef. Cook until the beef is heated through and slightly browned in spots.

Carefully slice the dinner rolls in half horizontally, keeping the rolls connected. Place the bottom half of the rolls in a 9x13-inch baking dish.

Spread mayonnaise evenly over the bottom rolls.

Add the warm roast beef in an even layer over the rolls.

Place the provolone cheese slices over the beef.

Spoon the sautéed peppers and onions evenly over the cheese.

Bake uncovered for 8 to 10 minutes, or until the cheese is melted.

Remove the pan from the oven and place the top half of the rolls over the filling.

Brush the tops with the melted butter and everything bagel mixture.

Return the sliders to the oven and bake for 5 more minutes, or until the tops are golden and warm.

Remove from the oven, slice into individual sliders, and serve warm.