Line two (3 1/2-quart) baking dishes with aluminum foil, letting the foil extend over the sides of each of the pans.
Spray the foil with nonstick cooking spray.
Spread 2 tablespoons of the enchilada sauce in the bottom of each pan.
In a medium saucepan, melt the butter over medium heat.
Add the rice mix, reserving the seasoning packet, and cook, stirring constantly, until the rice is lightly browned, about 2 minutes.
Stir in the water, the diced tomatoes with green chilies (and their juices), the onion, and the reserved seasoning packet.
Bring the mixture to a boil over medium-high heat.
Reduce the heat to low.
Cover and simmer the mixture until the rice is tender, about 15 minutes.
Spoon the rice mixture into a large bowl.
Add the cream cheese to the hot rice, stirring until the cheese is melted.
Add the chicken, the Colby Jack, the sour cream, the cumin, and the chili powder, stirring until combined.
Spoon 1/2 cup of the chicken mixture onto each of the tortillas.
Roll the filled tortillas up tightly.
Place the tortillas seam-side down in the prepared baking dishes.
Pour the remaining enchilada sauce over the tortillas.
Top the tortillas with the Pepper Jack cheese.
Cover one of the casseroles with foil and then freeze. Once frozen, using the foil overhangs as handles, transfer the tortilla casserole from the dish, wrapping it tightly in foil, and then wrapping it in plastic wrap. Freeze the casserole for up to 1 month.
Preheat the oven to 350 degrees F.
Bake the remaining casserole covered for 45 minutes.
Uncover and bake until hot and bubbly, about 15-20 minutes.
Garnish with the cilantro.
Serve with the tortilla chips and the salsa.