Rinse, clean and peel carrots, parsnips and beets. Halve the carrots, cut the parsnips into diagonal slices and cut the beets into thin wedges. Mix the vegetables on a baking tray lined with baking paper with olive oil, honey, coriander and chili flakes, season with salt and pepper. Bake in a preheated oven at 180 degrees (fan oven 160 degrees) on the second rack from the bottom for about 30 minutes.
Meanwhile, tear 100 g of blue cheese. Puree finely with yogurt, olive oil, lemon juice, sugar, salt and pepper in a tall container using a hand blender. Tear the remaining cheese (80 g) into small pieces.
Rinse spinach and spin dry. Remove the root vegetables from the oven and let them cool slightly. Fold in the spinach loosely. Arrange the salad in small bowls, drizzle with the dressing and serve sprinkled with the remaining shredded cheese.