Seared Skate with Baby Root Vegetables and Sauce Grenobloise

Name: Seared Skate with Baby Root Vegetables and Sauce Grenobloise
Ingredients: 8 small red beets with tops; 8 small golden beets with tops; Salt; 8 small white turnips with tops; 2 pounds spinach, cleaned, stems removed (can use 1 pound if beet and turnip greens are in good quality); 8 new potatoes; 1/2 cup olive oil, divided plus 2 tablespoons; 1 tablespoon fresh thyme, roughly chopped; Freshly ground black pepper; 2 large skate wings, skinned and filleted; 2 cups Wondra flour; 1/4 pound unsalted butter; 3 lemons, 1 segmented and 2 juiced; 3/4 cup demi-glace (chicken or veal); 4 slices white bread (not Wonder), cut into 1/2-inch cubes and toasted; 2 tablespoons flat-leafed parsley, roughly chopped; 2 tablespoons capers (non-pareil), drained