Preheat oven to 400 degrees F. Prepare a bowl with an ice bath for the beans.
Rinse and trim green beans. Bring a 2-qt pot of water to a boil.
Place green beans in a boiling pot for 2 minutes until they turn bright green. Once boiled for a few minutes, transfer beans to an ice bath for another few minutes to cool.
Spread blanched beans onto a parchment-lined baking sheet in one layer. Drizzle with 2 tablespoons olive oil, season with sea salt, and gently toss.
Roast in the preheated oven until beans are slightly shriveled for 20 to 25 minutes. Add minced garlic to green beans in the last 10 minutes of roasting.
Transfer roasted green beans to a serving plate. Add the pomelo segments and toasted walnuts then season with a pinch of sea salt to taste.