To make marinara sauce, heat olive oil in a saucepan over medium heat. Add garlic, basil and red pepper flakes; cook and stir for a minute or two until fragrant. Stir in sugar, vinegar, salt, and pepper. Pour in tomatoes with their juices and simmer over low heat for 15 minutes. Remove from heat and puree until smooth in food processor or blender.
Preheat the oven to 350 degrees F (175 degrees C).
Melt butter in a skillet over medium heat. Cook the zucchini in butter until browned and slightly tender. Season with red pepper flakes, salt, and pepper.
Spoon a generous amount of the zucchini mixture into each sandwich roll. Cover zucchini with about 1/4 cup marinara sauce per roll. Top with a handful of shredded mozzarella. Close the rolls, and wrap individually in aluminum foil.
Bake for 15 minutes in the preheated oven, until bread is heated through, rolls are soft, and cheese is melted.
Recipe adapted from http://allrecipes.com