In a bowl, mix the string beans, olive oil and salt. Sometimes I just spray the oil on the beans and then mix them to make sure they go on evenly. No need to go heavy on the oil or salt. Just a light brushing is good.
Place the beans on a piece of foil or other surface for easy clean-up, and then place the foil on a baking sheet.
Roast for 10 minutes, and then rotate the beans to brown the other side. I just move them around using a fork to shift their positioning. Roast for another 5 minutes.