Preheat oven to 350°F (175°C). Without separating the individual rolls, slice the entire slab of Hawaiian rolls in half horizontally, creating a top and bottom layer. Place the bottom layer in a greased 9x13-inch baking dish.

In a large skillet over medium heat, cook the breakfast sausage, breaking it into small crumbles, until browned and cooked through, about 6-8 minutes. Drain excess grease. Reduce heat to medium-low, pour beaten eggs into skillet with sausage. Gently scramble until eggs are just set but still moist, about 3-4 minutes. Remove from heat.

Sprinkle 1/2 cup of shredded cheddar cheese over the bottom layer of rolls. Spread the sausage and egg mixture evenly over the cheese. Top with remaining 1 cup of cheddar cheese. Place the top half of the rolls over the filling.

In a small bowl, mix melted butter with garlic powder, onion powder, smoked paprika, and black pepper. Brush or drizzle this seasoned butter mixture evenly over the top of the rolls, making sure to get some in the crevices.

Cover the baking dish with foil and bake for 15 minutes. Remove foil and bake for an additional 10-15 minutes, until the tops are golden brown and the cheese is melted and bubbly.

Remove from oven and let cool for 5 minutes. Garnish with chopped parsley if desired. Transfer the entire slab to a wooden board and serve warm, allowing guests to pull apart individual sliders.