Cook the pasta according the the package instructions.
In the meantime, prepare the sauce. Heat olive oil in a saucepan over medium heat. Whisk in the flour until incorporated. This will happen quick so watch for burning. Gradually pour in the milk, about ¼ a cup at a time, whisking continuously. Once all the milk is in, turn the heat down to low and allow to cook until the mixture is thick, this may take about 8-10 minutes.
Remove from the heat and add the nutritional yeast, garlic powder, onion flakes, cayenne and salt and pepper to taste. Stir until well combined.
Pour sauce of cooked pasta and sprinkle with sundried tomatoes and sage. Stir together and serve warm.