Summarize this article in one sentence.
Some dinner rolls may already come precut. If this is the case for your rolls, all you have to do is pull them apart in half. "Hawaiian" or sweet rolls would be great for this recipe! Open up the rolls, and place a slice of ham and Swiss on each bottom half. Cover the ham and cheese with the top half of the roll.  You may have to cut the cheese and then layer it inside the rolls to ensure that it fits.  Don't have Swiss or can't stand the taste? Cheddar, Colby jack, or Monterey jack instead! It is okay if the rolls are touching, but they shouldn't be crammed together either. If you don't have enough room on your baking sheet, set the remaining rolls aside and plan to bake them in a separate batch. If you have not already, melt the butter in the microwave or in a little saucepan on the stove. Pour it into a medium-sized mixing bowl, then add the onion flakes, mustard, Worcestershire sauce, and poppy seeds. Stir them together with a fork or whisk until everything is evenly combined. For a more complex flavor, use Dijon mustard instead of yellow mustard. During this time, the mixture will soak into the bread and give it more flavor. You are ready to bake the rolls when the butter starts to set. After 15 minutes, take a peek at the rolls. If the cheese is melted, you are ready for the next step. If the cheese is not melted, bake the rolls for another minute or two. They are ready when the tops turn golden and crispy. They are perfect for parties when you have to serve lots of people.

Summary:
Preheat your oven to 350°F (175°C) and line a large baking sheet with aluminum foil. Cut the dinner rolls in half with a bread knife. Place a slice of ham and Swiss cheese inside each roll. Arrange the rolls on a baking sheet, and set them aside. Combine the rest of the ingredients in a medium-sized mixing bowl. Pour the mixture over the sandwiches, then let them sit for 10 minutes. Cover the rolls loosely with aluminum foil and bake them for 15 minutes. Remove the foil, and bake the rolls for another 3 to 4 minutes. Serve the rolls straight out of the oven while they are still warm.