Preheat oven to 375F.
Bring a medium pot of water to a boil.
Slice zucchini into long thin strips on a mandolin. (You want them to be thin enough to roll, but not so thin they break).
Blanch the zucchini in the boiling water for a couple of minutes, until they begin to soften.
Shock the zucchini in cold water to stop it from cooking further.
In a medium bowl, combine the ricotta, mozzarella, onion, red pepper, garlic, red pepper, black pepper, salt and 1/4 c basil.
To assemble, scoop a heaping tablespoon of filling onto a strip of zucchini. Roll up the zucchini and place seam-side down in oiled baking dish. Repeat until all the zucchini and filling are used.
Pour marinara over the roll-ups, top with remaining 1/2 c mozzarella, crushed red pepper flakes and dried oregano (optional).
Bake at 375F until zucchini is cooked and cheese is bubbly, about 20 minutes. Garnish with fresh basil before serving.