Bring a large pot of salted water to a boil and prepare a large bowl with ice water next to it.
Once the water starts boiling, add in the green beans and boil for just 3-4 minutes, or until slightly softened yet still tender-crisp.
Using tongs or a large slotted spoon, quickly transfer your blanched green beans into the ice water. Allow them to bathe in the ice water for a minute or two, then drain very well and set aside.
Meanwhile, preheat your oven to 425 degrees f. Lightly spray or brush an oven-safe dish with cooking oil.
In a large bowl add the blanched beans, marinara sauce, oil, garlic, a pinch of sea salt and pepper. Toss very well to coat all the green beans.
Transfer your green beans to the prepared dish using a rubber spatula to get all of the sauce.
Roast for 15 minutes, or until the beans are tender and the sauce is bubbly.
Remove from the oven and top with your mozzarella cheese.
Return to the oven and broil for about 4 minutes, or until the cheese is melty and golden browned.
Sprinkle with fresh basil leaves if desired.
Enjoy immediately.