Chicken, Onion, and Mozzarella Sandwiches with Roasted Potatoes

Preheat oven to 400 degrees. Brush a rimmed baking sheet with oil. Place potatoes at one end and onion at other end; brush vegetables with oil and season with salt and pepper. Bake until potatoes are tender when pierced with a knife and onions are soft and browned, 30 minutes, flipping halfway through.

Meanwhile, in a large cast-iron or heavy skillet, heat oil over medium-high. Season chicken on both sides with salt and pepper. Cook chicken until browned and cooked through, 4 minutes, flipping once. Top each cutlet with 1 slice cheese, cover skillet, and cook until cheese is melted, 1 minute. Layer cutlets on bottom halves of rolls with onion, arugula, and parsley. Spread mayonnaise on top halves of rolls. Sandwich and serve with roasted potatoes.