In a large mixing bowl combine the chicken, taco seasoning, sour cream, cheddar and chilies. Place a few spoonfuls of the chicken mixture down the middle of each tortilla and roll up. Lay them in a prepared 9x 13 baking dish. Cut the velveeta into chunks and place into a skillet. Melt the velveeta with the rotel tomatoes over medium low heat until smooth. Pour over the enchiladas and bake at 375 for about 25-30 minutes until bubbling.