Preheat oven to 400 degrees. Line 2 baking sheets with parchment paper.
Place the butternut squash cubes in a large bowl and drizzle with olive oil to coat. Transfer to prepared sheet pan and spread out in one layer. Season with sea salt, pepper, and half the rosemary.
Place the apple cubes in the same bowl and drizzle with olive oil to coat. Repeat the same procedure as the squash.
Place the sheet pans in the oven and roast squash for about 30 minutes, turning halfway, until tender and slightly caramelized. Roast apples until just tender, about 20 minutes. Remove from the oven and allow to cool slightly.
Whisk together the balsamic vinegar and olive oil.
Thread the squash, apple, beet and arugula or spinach on a small skewer or toothpick. If you decide to use feta, wrap the cube of feta with a leaf of arugula/spinach and skewer. Arrange on a serving plate and drizzle with the vinegar and oil.
Notes
*other ideas include parsnips, carrots, sweet potatoes.