Preheat the oven to 400 degrees F (200 degrees C).

Heat a frying pan over medium heat. Add olive oil. Add tomatoes, garlic, Italian seasoning, red pepper, and salt. Cook, stirring often, until tomatoes have mostly broken down, about 5 minutes. Spread tomato mixture over the pizza crust.

Heat the same pan over medium-high heat. Add sausage and cook until browned, about 6 minutes. Remove cooked sausage from the pan and set aside, reserving grease in the pan. Add onion and fennel to the pan and cook until softened, about 5 minutes. Add spinach and cook until leaves begin to wilt, about 30 seconds.

Spread sausage and vegetable mixture over tomato-covered crust. Scatter dollops of ricotta cheese on top. Sprinkle with shaved Parmesan cheese.

Bake in the preheated oven until cheese is melted and top is beginning to brown, 8 to 10 minutes.