Heat the oven to 400 degrees F. In a large bowl, toss the squash with 3 tablespoons olive oil and season with salt and pepper. Transfer the squash to a baking sheet (reserve the bowl) and roast, cut-side down, for 25 minutes.
After 25 minutes, flip the squash so the other cut side is facing down. In the large bowl, toss the radicchio with 3 tablespoons oil, then add the radicchio and the figs to the baking sheet. Drizzle the honey over everything. Roast until the squash and radicchio are tender, 10 to 15 minutes more.
Meanwhile, in the same large bowl, stir together the red wine vinegar, coriander seeds, and 3 tablespoons olive oil. Season to taste with salt and pepper, then stir in the grapes.
When the vegetables are out of the oven, drizzle the dressing on top, spooning the grapes over, and scatter with mint. Scrape up the honey bits on the baking sheet and serve.