Preheat the oven to 425°F (220°C) and line a baking sheet with parchment paper or lightly grease it.
In a large bowl, combine the shredded cooked chicken, 2/3 cup salsa, 1 1/2 teaspoons ground cumin, and 1 teaspoon dried oregano. Stir until evenly mixed and set aside.
Prepare the Knorr Fiesta Sides Spanish Rice according to package directions (cover and simmer for 7 minutes) or prepare an equivalent homemade Spanish rice and remove from heat.
Stir the warm rice into the chicken mixture, then fold in 1 1/4 cups shredded Colby Jack cheese until combined.
Divide the filling evenly among the four flour tortillas. Roll each tortilla into a tight burrito, folding in the sides and placing seam-side down on the prepared baking sheet.
Brush each chimichanga with the remaining oil and bake in the preheated oven for 20 minutes, until golden brown and crispy.
Let the chimichangas rest briefly, then serve with desired toppings such as shredded cheese, sour cream, tomato, cilantro, green onion, lettuce, salsa, guacamole, and lime wedges.