How to Make It
Preheat oven to 425°F with racks in upper and lower thirds. Toss together carrots, 1 tablespoon of the oil, ½ teaspoon of the salt, and ¼ teaspoon of the pepper on a rimmed baking sheet. Toss together cabbage, remaining 2 tablespoons oil, ½ teaspoon of the salt, and ¼ teaspoon of the pepper on a second rimmed baking sheet. Roast, stirring carrots and cabbage halfway through and rotating baking sheets top to bottom, until carrots are golden brown and cabbage is golden and crispy, 24 to 28 minutes.
Meanwhile, cook farro in a large pot of boiling salted water until tender, 20 to 30 minutes. Drain and transfer to a large bowl.
Place ricotta and remaining ¼ teaspoon each salt and pepper in a food processor and process until very smooth. Spread ricotta mixture onto a platter and top with farro, carrots, and cabbage. Sprinkle with pistachios.