Without separating the individual rolls, slice the entire sheet of Hawaiian rolls in half horizontally so you have one large top layer and one large bottom layer. Set the bottom half, cut-side up, directly onto your lined baking sheet. Keeping the rolls connected is what makes this recipe so fast and foolproof.
Lay all 12 slices of sharp cheddar cheese evenly across the bottom half of the rolls so every single section gets full coverage. I like to slightly overlap the slices so there are no gaps once it melts. This is the step that turns simple rolls into an actual grilled cheese.
In a small bowl, stir together the melted butter, garlic powder, onion powder, and dried parsley until fully combined. This fragrant butter is what gives the tops their golden color and that irresistible savory aroma while baking. I always make a little extra because it disappears fast.
Place the top half of the rolls back over the cheese layer, cut-side down, so you've got one giant connected sandwich. Using your pastry brush, generously coat the top of the rolls with the garlic butter mixture, making sure to get every corner. Sprinkle a small pinch of flaky sea salt over the top.
Cover the tray loosely with foil and bake at 350°F for about 10 minutes, then uncover and bake for another 3–5 minutes until the tops are golden and the cheese is fully melted. The foil keeps the rolls soft while letting the cheese melt through before the tops get too dark.
Let the tray rest for 2–3 minutes before using a serrated knife to slice along the natural seams of the rolls into individual mini sandwiches. Serving them warm is key, since the cheese is at its gooiest right out of the oven. Arrange them on a platter and watch them disappear.