Cook the pasta in salted water until 1-2 minutes short of al dente based on package directions. Drain the pasta, reserving ⅔ cup of pasta water. Do not rinse the pasta.
While the pasta is cooking, season the shrimp with 1 teaspoon of cajun seasoning and set aside. Season the chicken with 2 teaspoons of cajun seasoning and set aside.
In a large skillet or Dutch oven, heat 1 tablespoon of oil in a large, over medium-high heat. Add the shrimp and cook for 1-2 minutes per side or until opaque. Remove the shrimp from the pan and set aside.
Add another 1 tablespoon of oil to the pan and brown the chicken on all sides until almost cooked through (about 5-6 minutes). Remove the chicken from the pan and set aside.
Add the remaining 1 tablespoon of oil to the pan and brown the sausage slices on both sides for 1-2 minutes.
Then add the onion and bell peppers to the pan with the sausage and cook for 4-5 minutes or until the vegetables soften.
Add the garlic and saute for 30 seconds to 1 minute or until fragrant.
Pour the canned tomatoes, reserved pasta water or chicken broth, pasta, remaining cajun seasoning, thyme, oregano, and cooked chicken to the pan and bring to a gentle boil. Reduce the heat to low, cover the pan, and simmer for 8-10 minutes or until the sauce has thickened and the pasta is tender.
Add the cooked shrimp to the pan and cook for 2-3 minutes or until the shrimp are heated through.
Serve hot, garnished with chopped parsley if desired.