Soak cashews in 1 cup of boiling water for 30 minutes. Drain, reserving 1/2 cup of the soaking liquid.
Combine the soaked cashews, garlic, nutritional yeast, salt, and the 1/2 cup of reserved soaking water in a high power blender. Blend until smooth and creamy. Set aside or refrigerate until ready to use.
In a large pot, bring water to a boil and add salt to taste. Add the lasagna sheets and cook for 10 minutes, stirring often to keep them from sticking together.
While the pasta cooks, prepare the filling. Combine all the ingredients in a medium bowl and mix well. Set aside until ready to use.
Once the pasta sheets are cooked, drain them and run them under cold water (if any of the sheets are stuck together, separate them carefully). Set them aside.
Preheat oven to 375. Combine the prepared tomato sauce and red pepper flakes and pour on the bottom of a 10 1/2 x 7 1/2 inch baking dish. Spoon about half of the cashew cream over the sauce.
To prepare the cannelloni, place about a tablespoon and a half of filling on each pasta sheet and carefully roll each one. Arrange them on the baking dish, over the tomato sauce and cashew cream. Cover tightly with aluminum foil and bake 45 minutes.
Drizzle with the remaining cashew cream before serving. Keep warm.