Add the bell peppers, celery, onion, garlic, cajun seasoning, and thyme. Sauté for 6 minutes, stirring occasionally, until the onions are softened. Add in the flour and cook while stirring for 3 - 5 minutes until the flour starts to turn golden brown.
Add the tomatoes, chicken broth, and rice. Stir to combine and cover with a lid. Bring to a low simmer for about 20 - 25 minutes, stirring occasionally or until the rice is cooked. Add in the shrimp and cook for 5 - 7 minutes more until firm.
Season with salt and pepper to taste. Use a slotted spoon to plate to avoid over-saucing. Spoon the remaining sauce over top to your liking.