Preheat the oven to 400 degrees F and line a baking sheet with parchment paper.
Combine the farro with 4 cups of water and 1 teaspoon salt in a large saucepan. Bring to a boil, then lower the heat and simmer, uncovered, until the farro is tender, about 30 minutes, adding more water if needed. Drain and pour into a large bowl.
Place the red pepper slices on the prepared baking sheet and toss with 2 teaspoons olive oil, 1/4 teaspoon salt and a few grinds of black pepper. Roast for 20 minutes, turning once halfway through. Set the peppers aside to cool slightly.
Meanwhile, whisk together the lemon juice, vinegar, garlic, oregano, 1 teaspoon salt and 1/2 teaspoon pepper in a small bowl. Slowly whisk in the remaining 3 tablespoons olive oil. Pour over the hot farro, stir well and cool to room temperature, stirring occasionally.
Add the cucumber, tomatoes, red onion, parsley and olives and roasted peppers to the bowl with the farro. Stir until combined, then gently fold in the feta. Serve at room temperature, or store in the refrigerator, covered, for up to 3 days, before serving.