In a large skillet over medium-high heat, heat the olive oil.
Coat the roasts on all sides with the Cajun seasoning and place one roast at a time into the skillet. Sear on all sides before transferring to a large slow cooker.
Top the roasts with tomatoes and green chillies, red bell pepper, celery, onion, garlic powder, and salt. Mix to combine.
Cover the slow cooker and cook on low for 6 to 8 hours or until the meat is tender. Serve with rice or noodles.
To freeze, place the seared roasts in an airtight container with the remaining ingredients except the rice/noodles. Freeze for up to 6 months. Thaw in the refrigerator before cooking according to above directions.