Preheat the oven to 350°F.
Prepare the bow tie pasta according to the package directions. Cook until al dente, then drain and set aside.
Cook the bacon in a skillet until crisp.
Remove the bacon from the skillet, chop it into pieces, and reserve a small amount of the bacon grease.
Slice the boneless chicken thighs into small pieces.
Coat the chicken pieces with the ranch dressing mix.
In a skillet, heat 1 to 2 tbsp of the reserved bacon grease.
Add the seasoned chicken, minced garlic, and diced bell pepper.
Cook until the chicken is fully cooked and the bell pepper has softened.
Drain any excess grease from the pan, leaving the chicken and bell pepper mixture in the skillet.
Add 1 jar Alfredo sauce, the evaporated milk or regular milk, and 1 tsp ranch dressing mix to the skillet.
Stir until the sauce is smooth and evenly combined with the chicken mixture.
Spread 1/2 jar Alfredo sauce over the bottom of a large casserole dish.
Add a layer of cooked bow tie pasta over the sauce.
Spoon a layer of the chicken Alfredo mixture over the pasta.
Add a layer of diced Roma tomatoes.
Sprinkle with a portion of the chopped bacon and shredded Mexican cheese blend.
Repeat the layers until the pasta, sauce, tomatoes, bacon, and cheese are used, making approximately three layers.
Cover the top of the casserole with the remaining sauce, shredded cheese, and chopped bacon.
Bake uncovered for 30 minutes, or until the casserole is hot, bubbly, and the cheese is fully melted.
Remove the casserole from the oven and allow it to cool for several minutes before slicing or serving.
Serve warm.