Preheat the oven to 350 degrees. Cut the rolls horizontally so that there is a top and bottom layer. Place the bottom layer of rolls into a 9x13 casserole dish.
Spread an even layer of BBQ sauce on the bottom layer of the rolls, then place a layer of roast beef on top. Next, evenly spread the cheese sauce on top of the roast beef and place the top layer of rolls on.
In a small bowl of melted butter add the dehydrated onions and parsley then stir to combine. Baste the mixture on top of the sliders.
Bake at 350 for 10-15 minutes until the tops are slightly toasted and the contents of the sandwich are hot. Serve & enjoy!