Preheat oven to 425. Add a teaspoon of olive oil to a large baking dish and add the potatoes, squash, rosemary, salt, pepper, crushed red pepper flakes and remaining olive oil. Toss lightly to coat. Roast for 40-45 minutes, or until the potatoes are fork tender. Remove from the oven and allow to cool for 5 minutes.
In a large bowl, add the potatoes, spinach/arugula mix and feta. Toss lightly to combine. Serve immediately.