Preheat oven to 350◦ F. Toss whole beets together with olive oil, chopped garlic, thyme and bay leaf on a sheet pan. Season with salt and pepper. Cover tightly with foil and roast for 1-1/2 hours. Let cool slightly.
Peel and cut the beets into 1/2-inch dice. Toss with 1 tablespoon olive oil, parsley, marjoram, salt and pepper. In a separate bowl, marinate the goat cheese in 1/2 tablespoon olive oil. Allow beets and goat cheese to rest at room temperature.
When ready to serve, season arugula with 1 tablespoon olive oil, salt and pepper. Top with beets and garnish with marinated goat cheese.