Preheat the oven to 400 degrees. Place diced sweet potatoes in a single layer on a sheet pan, and drizzle with olive oil and salt. Roast for 25-30 minutes. Carefully turn halfway through the cooking time to ensure even browning.
While the sweet potatoes roast, combine remaining ingredients to a saucepan and turn heat to medium-low. Whisk over low heat until smooth. Add a bit more water as needed. Drizzle potatoes with sauce before serving.