Preheat your oven to 350°F.
Lightly oil or butter a large casserole dish.
Bring a large pot of salted water to a boil.
Add pasta and cook, stirring occasionally, according to package directions until al dente. Drain.
While pasta is cooking, melt butter in a large skillet over medium heat. Add onion and bell pepper; cook, stirring occasionally. If using freeze dried vegetables, add ¼ cup of water to the pan.
Add garlic, paprika, and oregano. Cook, stirring occasionally, until tender and fragrant.
Stir in diced tomatoes with juice and mild chile peppers until combined.
Add cheese and stir until melted, 5 to 10 minutes.
Remove from heat and combine with cooked pasta and chicken in the prepared baking dish.
Bake in a preheated oven for about 20 minutes until heated through.
Serve warm.