Heat the olive oil over medium high heat and add the sausage bits. Cook just until lightly browned, about 1-2 minutes per side and set aside.
Add the onion and garlic and saute for 1-2 minutes or until fragrant and soft.
To a lightly greased 13x9" casserole dish, add the cooked sausage, onions, garlic, cauliflower rice (still frozen), bell peppers, kidney beans, diced tomatoes (without the juice), cajun seasoning and a generous pinch of salt and pepper. Mix to combine and break up any cauliflower rice chunks. Press lightly down.
Bake for 20 minutes or until the cauliflower rice is tender and hot, and the sausage is cooked through.
Make this sausage casserole in one pan and cut down on cleaning up by using a cast-iron skillet. This way you can go from stovetop to oven.
You can swap the turkey sausage for Cajun sausage, smoked sausage, or another sausage of your choice.