Pre-heat oven to 350 degrees and place bell pepper halves in a single layer, facing up, in a 9 x 13 baking dish; set aside.
Heat a large skillet over medium-high heat and spray with cooking spray. Add Italian sausage to the pan and heat until browned, about 9-11 minutes, using a wooden spoon to break the sausage into bite-sized crumbles.
Pour Green Giant Riced Kohlrabi into the pan, along with garlic, oregano, salt, chili flakes and fennel seeds. Cook until kohlrabi is warmed through, about 2-3 minutes.
Add the tomato sauce to the pan and stir well; remove from heat.
Begin stuffing peppers with equal parts of the sausage mixture (about ⅓ cup each) until each pepper is evenly stuffed. It's ok to over-fill them. Sprinkle pan evenly with shredded cheese then bake until peppers are cooked through and the cheese is melted and bubbly, about 30 minutes.