Preheat oven to 350°F (175°C). Lightly spray one or more baking sheets with nonstick spray and set aside.
Heat a medium nonstick skillet over medium heat. Add 1 lb ground beef and break it up with a wooden spoon as it cooks.
When the beef is almost cooked through, add 1 ounce taco seasoning and 1/4 cup water. Stir to combine and continue cooking until the beef is fully cooked and reaches 160°F, about 8–10 minutes total from when you started cooking. Transfer the beef to a paper-towel-lined plate to drain and set aside. Wipe out the skillet.
Return the skillet to medium-high heat and add 1 Tablespoon oil. Cook the corn tortillas in batches, flipping frequently with tongs, until they are browned and as crisp as you like. Transfer cooked tortillas to a paper-towel-lined plate to drain. (You should cook all 16 tortillas.)
Heat the 16 ounces refried beans in a microwave-safe bowl (or in a small saucepan) until just soft and spreadable. Stir to ensure smooth consistency.
Assemble the pizzas on the prepared baking sheet(s). For each pizza: place one cooked tortilla as the bottom, spread a thin layer of refried beans on it, and top with 1–2 tablespoons of the cooked beef. Place a second tortilla on top to form a stack.
On the top tortilla of each stack, spoon about 1 tablespoon enchilada sauce (divide the 10 ounces among the pizzas as you prefer). Sprinkle diced Roma tomatoes, then top generously with shredded Mexican blend cheese. Finish by sprinkling chopped green onions over each.
Bake the assembled pizzas in the preheated oven for 6–7 minutes, or until the cheese is fully melted and bubbly.
Remove from oven and let cool for 1–2 minutes. Cut and serve.