Preheat the oven to 450F or 425F convection. Line a baking sheet with parchment paper.
In a medium pot, add the farro and enough water to cover by at least 2-inches. Bring to a boil, then reduce the heat to medium-low and simmer rapidly for 25-30 minutes, or until tender (grains have burst open a bit). Drain and transfer to a large bowl.
Add sweet potatoes to ¾ of the baking sheet and onions to the remaining ¼. Drizzle 2 tablespoons olive oil mostly over the sweet potatoes and a bit onto the onions. Sprinkle sweet potatoes with about ½ teaspoon salt, smoked paprika, and garlic powder and sprinkle onions with ¼ teaspoon salt. Toss each to coat. Bake in the oven for 20-25 minutes or until browned in spots.
Add sweet potatoes to the large bowl along with the fennel, herbs, cheese, remaining ¾ teaspoons salt, remaining ¼ cup olive oil, and vinegar. Toss to coat. Taste and add more salt or vinegar if it tastes flat.
Serve it up topped with plenty of nuts and/or seeds.