3 red beets (about 1 to 1 1/4 pound)
1 large sweet potato, peeled and cut into chunks (about 1 pound)
1 1/2 tablespoons olive oil, plus 1 tablespoon, divided
1/8 teaspoon salt
1/8 teaspoon black pepper
1 medium yellow onion, diced
2 stalks celery, diced
2 cups low-sodium vegetable broth
Juice of 1 lime
1 tablespoon fresh minced ginger
1/3 cup fresh chopped cilantro
1/4 teaspoon cayenne pepper
1 (15-ounce) can light coconut milk