Preheat oven to 400 degrees. Arrange half the bag of tortilla chips on a baking sheets, sprinkle with half the diced roasted chicken, half the shredded Oaxaca cheese and half the diced roasted tomatoes. Add second layer of remaining tortillas chips and top with remaining diced roasted chicken, shredded cheese and diced tomatoes. Bake for 10 minutes until cheese is bubbly and chicken has warm through. While nachos bake in a bowl toss together crumbled queso fresco, minced red onion and cilantro. Remove nachos from oven, top with queso fresco mixture and drizzle with crema Mexicana, serve warm.