Move a rack in your oven to the upper third of the oven and then preheat to 425 degrees F.
Put a large oven-safe skillet on the stove at medium-high heat. Pour in the olive oil.
Add in the chopped onion and stir until the onion is transparent -- about 4 minutes. Add in the garlic and stir for another 30 seconds.
Coin the smoked sausage and add to the skillet. Cook over high heat until lightly browned or about 4-6 minutes.
Add in the chicken stock, undrained fired roasted diced tomatoes (Italian roasted tomatoes for less spicy), thyme, rosemary, sage, parsley flakes, garlic powder, seasoned salt and pepper (to taste), and uncooked gnocchi. Stir until everything is well combined. Gently stir in the spinach and make sure it's covered with liquid.
Top with mozzarella and Parmesan cheese and place in the oven.
Bake for 17-22 minutes. If desired, turn on the broiler and then broil for another 2-3 minutes for a delicious crispy top.
Remove from the heat, top with additional salt, pepper, and some chopped thyme if desired. Enjoy immediately.