1. Heat oven to 415 F. Line a baking sheet with parchment paper.
2. Cut the squash in half lengthwise, then cut each piece in half again, making 4 large chunks.
3. Remove the skin with a vegetable peeler or sharp knife.
4. Cut the butternut squash into 1-inch cubes and set aside.
5. In a large mixing bowl, combine olive oil, balsamic vinegar, rosemary and salt.
6. Add butternut squash cubes and toss until squash is evenly coated.
7. Pour the mixture onto the lined baking sheet and spread evenly. (NOTE: Keep the mixing bowl for the final step.)
8. Bake for 35-40 minutes, or until squash edges begin to brown.
9. Remove from oven and let cool for 10 minutes.
10. Add the roasted squash back into the large mixing bowl. Toss in the crumbled feta and serve.

NOTE: Save the seeds! Clean them off under running water with a strainer to remove the fibrous strands. Roast them in the oven with olive oil, garlic powder and salt. Add to salads or eat them on their own.