Preheat oven to 450°. Cook beans in a large pot of boiling salted water until crisp-tender, about 2 minutes. Drain, transfer to a bowl of ice water, and let cool.
Drain and pat dry.
Toss beans and oil on a rimmed baking sheet; season with salt and pepper. Roast, tossing occasionally, until tender and lightly charred in spots, 10–15 minutes.
Meanwhile, whisk soy sauce, sorghum, benne seeds, and cumin in a large bowl; season with salt and pepper. Add warm beans and toss to coat.