Preheat the oven to 350 degrees F (175 degrees C).
Cut the stems from the green beans. Place the beans and the sliced mushrooms on a baking tray. Drizzle with olive oil, and sprinkle with salt and pepper.
Roast in the oven for 8-10 minutes. Remove from the oven and turn the vegetables on the tray. Roast for an additional 5 minutes.
