Dice the potatoes into 1-inch cubes. (No need to peel them!) Spread the cubed potatoes on a baking sheet.
Peel and dice the beets and carrots into 1-inch cubes. Add to the baking sheet.
Peel, remove seeds, and dice butternut squash. Or just purchase it already prepared this way from the produce section of the grocery store and save yourself some time. (This is one veggie I like to buy already chopped when available.) Add to the baking sheet.
Peel and dice onion. Add to the baking sheet. Use a spatula to spread all the veggies in a single layer.
Drizzle olive oil over everything. Sprinkle with salt.
Bake for 20 to 25 minutes. Potatoes, squash, and carrots should be tender when finished.
Remove from oven and sprinkle rosemary over the vegetables before serving.