Step 1: Preheat your oven to 400°F (200°C). On a large baking sheet, toss the sweet potatoes, carrots, and red onion with 2 tablespoons of olive oil, dried thyme, salt, and pepper.
Step 2: Roast the vegetables for 25-30 minutes, tossing halfway through, until they are tender and caramelized at the edges.
Step 3: While the vegetables roast, combine the farro and vegetable broth in a medium saucepan. Bring to a boil, then reduce heat to low, cover, and simmer for 15-20 minutes or until the liquid is absorbed and grains are tender.
Step 4: In a small bowl, whisk together the remaining olive oil, balsamic vinegar, Dijon mustard, and maple syrup to create the dressing.
Step 5: In a large mixing bowl, combine the warm farro, roasted vegetables, and baby arugula. Pour the dressing over the top and toss gently to combine.
Step 6: Garnish with toasted walnuts if desired and serve warm or at room temperature.