These are great with fresh basil, if you use it make sure you leave it off for roasting. Add it after the beans are done cooking, just toss with the roasted beans.
Dry green beans well and spread on a rimmed baking sheet. Toss with olive oil (use your hands), so that all the beans are coated. Sprinkle with salt, pepper, basil. Toss again to coat.
Roast for 10 minutes, toss, and continue to roast for 5 more minutes. Immediately sprinkle with parmesan and serve.