Brown sliced sausage in a large skillet over medium-high heat for 5 minutes; remove and set aside.
In the same skillet, add minced garlic and diced bell pepper, cooking for 2 minutes.
Stir in frozen cauliflower rice and marinara sauce, then return sausage to the pan and simmer for 8 minutes.
Top with shredded mozzarella, cover, and cook for 2 minutes until melted.