Roasted squash, cauliflower, beets, and onion prove salads aren't just for summer.
Arrange the racks in the upper and lower thirds of the oven; preheat to 425°. Arrange the squash on one half of a large rimmed baking sheet; arrange the cauliflower on the other half. On another large rimmed baking sheet, arrange the beets on one half and the onion on the other.
Drizzle the squash and cauliflower with 1 tbsp. oil. Drizzle the beets and onion with 1 tbsp. oil. Season the vegetables with salt and pepper. Toss the vegetables, keeping each vegetable on its half of the sheet.
Roast until the onion is crisp-tender, 10 to 15 minutes; transfer to a plate. Spread the beets out on the baking sheet. Toss the squash and cauliflower, keeping each vegetable on its own half of the sheet. Rotate the sheets and roast until the vegetables are tender, about 15 minutes more. Let cool slightly.
In a small bowl, whisk the remaining 4 tbsp. oil with the lemon juice and chopped dill; season the dressing.
In a medium bowl, toss the lettuce with 3 tbsp. of the dressing. Schmear the hummus on the plates. Top with the lettuce, roasted vegetables, feta, and olives. Drizzle the salads with the remaining dressing.