Roasted green beans can be reheated in the microwave. However, the texture is a little better if they're eaten soon after cooking. If cooking for guests, you can part-roast the beans in advance, then just before serving, add the feta, and roast for a further 5-10 minutes.
Nutritional information is approximate, and will depend on your exact ingredients. Please calculate your own nutritional values if you require accuracy for health reasons.