01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - In a large mixing bowl, combine green beans with olive oil, minced garlic, salt, black pepper, and optional red pepper flakes; toss until thoroughly coated.
03 - Spread seasoned green beans in a single layer on the prepared baking sheet.
04 - Roast in the oven for 15 minutes, stirring once halfway through, until beans are tender and beginning to brown.
05 - Sprinkle shredded mozzarella and grated Parmesan evenly over the roasted beans.
06 - Return baking sheet to the oven and roast for an additional 5 minutes, or until cheese is bubbling and golden.
07 - Remove from oven and garnish with chopped parsley if desired; serve immediately.