Preheat oven to 400 degrees F (200 degrees C). Line a baking sheet with parchment paper and grease with cooking spray.

In a large bowl, combine ground turkey, egg, Italian seasoning, 1/2 teaspoon salt, 1/2 teaspoon black pepper, red pepper flakes, breadcrumbs, parmesan cheese, and parsley.

Mix until evenly incorporated.

Form the mixture into golf ball-sized meatballs and place them on one side of the prepared baking sheet.

Scatter cherry tomatoes around the meatballs on the baking sheet.

Place small red potatoes in a single layer on the other side of the baking sheet.

Drizzle everything with olive oil.

Season the potatoes with the remaining salt and pepper.

Roast in the preheated oven for 20 minutes, or until the potatoes are soft enough to smash.

Gently push down on the potatoes with a potato masher to smash them.

Drizzle the smashed potatoes with a bit more olive oil and sprinkle with chopped rosemary.

Return the baking sheet to the oven and roast for another 10 minutes.

Remove from the oven and top the meatballs and tomatoes with sliced mozzarella cheese.

Place the baking sheet under the broiler until the cheese is melted through, about 1 minute.

Top with sliced fresh basil leaves.

Serve immediately.