Preheat the oven to 400°F.
Place each beet on a piece of aluminum foil, drizzle generously with olive oil, and sprinkle with sea salt and freshly ground black pepper. Wrap the beets in the foil and roast on a baking sheet for 40 to 90 minutes, or until soft and fork-tender. The cooking time will depend on the size and freshness of the beets. Remove the beets from the oven, remove the foil, and set aside to cool. When the beets are cool to the touch, peel off the skins. I like to hold them under running water and slide the skins off with my hands.
Slice the beets into halves, quarters, or bite-sized pieces, and place them in the fridge until ready to use.
Make the lemon vinaigrette dressing according to this recipe, omitting the thyme, and adding the coriander, honey, and cumin.
Arrange the beets, arugula, feta and pistachios on a platter. Drizzle with some of the dressing and season with salt and pepper. Top with microgreens, if desired, and serve.