Adjust rack to top position (top and middle positions for 4 servings) and preheat oven to 450 degrees. Wash and dry produce.

Dice potatoes into ½-inch pieces.

In one oven-ready tray, toss potatoes with a drizzle of oil, half the garlic powder, salt, and pepper. Roast on top rack (be sure your oven has preheated!) until browned and tender, 20-25 minutes. (For 4 servings, divide everything between two trays, using a drizzle of oil in each tray; bake side by side on top rack.)

Pat chicken* dry with paper towels; season all over with salt and pepper.

Add marinara to remaining oven-ready tray; arrange chicken on top and drizzle with olive oil. (For 4 servings, divide everything between remaining two trays, using a drizzle of olive oil in each tray.)

Bake on top rack (side by side with potatoes) until chicken is golden brown and cooked through, 15-20 minutes. (For 4, bake trays with chicken side by side on middle rack, 18-22 minutes.)

In the last 1-2 minutes of cooking, carefully sprinkle mozzarella over chicken; return to oven and bake until cheese melts.

While potatoes and chicken bake, in a small bowl, combine mayonnaise, remaining garlic powder, 1 tsp water (2 tsp for 4 servings), salt, and pepper; set aside.

Halve baguettes lengthwise and toast until golden. TIP: You can toast in the oven if you like.

Divide chicken between bottom baguette halves; spoon marinara from tray over chicken. Close to form sandwiches.

Divide sandwiches between plates; serve with roasted potatoes and garlic aioli on the side for dipping.