Preheat the oven to 375°. In an 8-inch square nonreactive baking dish, toss the beets with the garlic, lemon juice, lemon zest, oil, and sugar. Season with salt and pepper and spread the beets in a single layer. Spray an 8-inch piece of parchment paper lightly with olive oil cooking spray and set it oiled-side down on the beets. Cover tightly with foil and roast, shaking the pan occasionally, for about 40 minutes, until the beets are tender. Serve the beets warm or hot.