Place the squash on a rimmed baking sheet. Drizzle with 1 tablespoon of the olive oil, season with 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper, and toss to coat. Arrange into a single layer. Roast, flipping halfway through, until browned and tender, about 30 minutes total. Meanwhile, cook the farro, toast the pumpkin seeds, prepare the dressing, and sear the radicchio.