Preheat oven to 400°F. Drizzle red and golden beets with olive oil, then wrap red beets in one sheet of aluminum foil and golden beets in a separate sheet. Place both foil packets on a baking sheet and roast until the beets are tender, about 1 hour. Once removed from the oven, allow them to cool, then remove the skin using a paper towel.
While the beets are roasting, cut the halloumi into 1-inch cubes and pat dry with a paper towel. Add 2 tablespoons of olive oil in a large skillet over medium-high and add the cheese cubes. Cook a few minutes until the bottoms are golden brown. Turn the cubes over with a spatula and finish browning the other sides. Remove the cubes to a bowl, and season with salt, ground pepper, and red pepper flakes.
To assemble, thinly slice the roasted beets on a mandolin. Toss the Red RomaBlend with the fresh lemon juice, olive oil and season with salt and pepper. Arrange the beets, salad greens and halloumi cubes on a serving platter, keeping each salad component separate. Throw a handful of walnuts on top and serve.