Preheat the oven to 425.
Add the beets and sweet potatoes to a large sheet pan on opposite sides of the pan. Drizzle with the olive oil, then season with the dill, salt, garlic powder and pepper. Toss each separately then place in the oven for 30-35 minutes, until roasted and browned. Toss a few times while roasting.
While the sweet potatoes and beets roast, make the tzatziki. First, drain the liquid from the cucumber using a cheesecloth or paper towels. Next, add the yogurt, strained cucumber, dill, mint, olive oil, garlic, lemon juice, salt and pepper to a medium bowl. Whisk to combine. Place it in the refrigerator until ready to use.
Next, add the chopped beet greens to a bowl, drizzle with a little olive oil and some lemon juice. Season it with some salt and toss.
To serve, spread the tzatziki onto a plate, then in layers, add some greens, some sweet potatoes, some beets and repeat the layers until all of it is used up. Top with feta, sunflower seeds, fresh dill and pepper.
