Oven Roasted Potatoes and Green Beans

1 pound potatoes, diced large (I prefer the smaller potatoes, i.e. fingerling, small red, small gold.)
1/2 large onion, sliced
1 pound string green beans, ends removed
1/8 cup good olive oil
1 tsp salt, plus more to taste
1/2 tsp ground black pepper

Preheat oven to 425F.
In a large bowl, combine the potatoes and onions.
Toss the potatoes and onions with olive oil to coat.
Sprinkle salt and pepper.
Transfer the coated potatoes and onions to a baking sheet.
Bake in the preheated oven for 25-30 minutes, until the potatoes are tender.  Toss once while cooking, at the half-way mark.
After the potatoes are tender, toss in the string beans to the pan.
Bake for another 10-15 minutes, until the beans are tender.
Remove from the oven and add more salt and/or pepper if you want.
Adapted from The Vanilla Bean Blog who adapted it from Ina Garten and The Joy of Cooking