1. Preheat oven to 425 degrees. Divide sweet potatoes and garlic between 2 rimmed baking sheets. Drizzle with 3 tablespoons oil; season with salt and pepper. Toss to coat and spread into a single layer. Roast, flipping once, until tender and caramelized, about 30 minutes.

2. Meanwhile, cover farro with 4 inches water in a medium saucepan. Bring to a boil, then reduce heat and cook until tender, 30 to 35 minutes. Drain; toss with remaining 2 tablespoons oil in a large bowl. Season with salt.

3. When cool enough to handle, remove garlic from peels and mash with lemon zest and juice in a small bowl. Add garlic mixture, sweet potatoes, dill, and sprouts to farro; stir until combined. Season with salt and pepper, and garnish with sprouts.