Preheat the oven to 425° F and line a baking sheet with parchment paper
Pour the green beans into a colander and rinse them to get rid of any ice that's formed on them. Pat dry with a clean kitchen towel or a paper towel.
Add the green beans to your baking sheet and drizzle on the oil. Add the garlic, salt, and peppercorns, and toss well on the baking sheet. Then, spread them out into a single layer, spacing them as much as possible.
Bake for 16 to 20 minutes, until the green beans are cooked to preference.
Transfer the roasted frozen green beans to a serving dish, top them with the almonds, and serve.
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Notes
If you double this recipe, also be sure to use 2 baking sheets. You want to spread the frozen green beans out on the baking sheet(s) as much as you can. The less they're touching each other, the better they'll cook up.Make sure you don't skip rinsing and drying the beans. That will help prevent them from turning mushy when you cook them.Leftovers will keep for 3 to 4 days in the refrigerator.