Roasted Green Beans with Mushrooms, Balsamic, and Parmesan

I wanted to try this recipe, I found on pinterest.  The original post is here.  Here's my version.

Roasted Green Beans with Mushrooms, Balsamic, and Parmesan
(Makes 4-6 servings, recipe created by Kalyn)

Ingredients:
8 oz. mushrooms, sliced in 1/2 inch slices (I used white button mushrooms)
1 lb. fresh green beans, I used the steam in bag ones, I found in the produce section.  They were the only ones available.
1 1/2 T olive oil
1 T balsamic vinegar
salt and fresh ground black pepper to taste
2 T finely grated parmesan cheese

Instructions:

Preheat oven to 450F/230C. Wash mushrooms and let drain (or spin dry in salad spinner, which is what I did.) While mushrooms are drying, trim ends of beans and cut beans in half so you have bite-sized pieces. (Mine were pre-trimmed and washed.) Cut mushrooms into slices 1/2 inch thick.

Put cut beans and mushrooms into a Ziploc bag or plastic bowl. Whisk together olive oil and balsamic vinegar and pour over, then squeeze bag or stir so all the beans and mushrooms are lightly coated with the mixture. Once my oven was at 450F, I  arranged on large cookie sheet, spreading them out well so beans and mushrooms are not crowded. Roast 20-30 minutes, starting to check for doneness after 20 minutes. Cook until beans are tender-crisp, mushrooms are cooked, and all liquid on the pan from mushrooms has evaporated. Season beans to taste with salt and fresh ground pepper, then sprinkle with finely grated Parmesan. Serve hot.