Heat the olive oil in a large skillet over medium heat. Add the sausage slices and cook until browned on both sides, about 5 minutes. Remove the sausage to a plate and set aside.
Add the onion, bell pepper, and celery to the same skillet. Cook until the vegetables soften, about 4 minutes. Stir in the garlic and cook for 1 minute more.
Add the rice and Cajun seasoning. Stir to coat the rice with the spices and vegetables. Pour in the drained tomatoes and chicken broth. Bring the mixture to a boil.
Reduce the heat to low, cover the skillet, and simmer for 15 minutes until the rice is almost tender. Return the sausage to the skillet and stir gently.
Nestle the shrimp into the rice mixture. Cover and cook for 5 to 7 minutes until the shrimp turn pink and the rice is fully cooked. Season with salt and pepper if needed.
Remove from heat and sprinkle with sliced green onions before serving.