Cut rolls in half and lay bottom half of rolls into a 9"x13" pan. Set roll tops aside.
Fold slice of roast beef in half, to fit onto roll, and place it on the roll. Top with slice of cheese. Repeat these steps for remainder of rolls.
Sprinkle fried onions over top of the cheese topped rolls. You can use as little or as much of the onions as you like. I used about half of the container.
Place the roll tops onto the rolls in the pan.
for the sauce
Melt the butter in a glass measuring cup and stir in the remaining sauce ingredients.
Once everything is thoroughly mixed, slowly pour the sauce over top of all of the rolls. You should have enough sauce that you can pour over each of the rolls twice.
Cover the pan with foil and slide into the oven to bake for 8 minutes.
Remove the foil and cook for another 3-4 minutes (until the cheese has slightly melted).
Remove from oven and serve.
It's easier to serve these if you cut them apart. You can leave them in the pan as you cut them.
Recipe by My Man's Belly at https://mymansbelly.com/2017/01/31/roast-beef-and-swiss-sliders/