Dice the onion and bell pepper.
Place the diced onion and pepper onto a sheet of aluminum foil and drizzle olive oil on top.
Wrap the aluminum foil around the vegetables, place the pouch on the grill, and grill until cooked (10-20 min). Set aside.
Slice the potato rolls in half lengthwise.
Make your sliders by adding roast beef, cheese, grilled onion and bell pepper, and remoulade sauce to the rolls.
Place the sliders on the grill over indirect heat and grill until the bread is crisp and the cheese is melted. (You can place the sliders directly onto the grill or wrap them in aluminum foil first.)