Winter squashes, such as acorn and butternut, can be tricky to work with because their tough skin is hard to peel. Preparing squash this way—stuffed with a savory filling and roasted—puts that sturdy shell to good use. The rice should be quite moist after it cooks in step 3; it provides good contrast to the squash and helps the stuffing mixture stay together without becoming chewy or dry during baking.
1) Cut each acorn squash in half through the stem. Trim the stem and remove and discard the seeds (keep the skin on). Bring a large saucepan or pot of water to a boil. Add the squash halves and cook until the squash is slightly soft when pierced with a fork, 15 to 20 minutes. Remove from the water and drain well. Set aside until cool enough to handle.
2) Meanwhile, bring 1½ cups water to a boil in a small saucepan. Add the wild rice medley and cook, covered, over medium heat for 25 minutes. (Alternatively, follow the cooking instructions on the rice package, using a bit more water than called for so that the rice is moist after steaming.) Remove from the heat and set aside.
3) Use a spoon to scoop out the inner edges of each cooled squash half to create a wider and deeper hollow for the stuffing; leave about half of the squash flesh attached to the peel.
4) Reserve the scooped-out squash flesh for the stuffing. Set the squash shells aside. Preheat the oven to 350°F. In a skillet with a lid, combine the vegetable broth, onion, garlic powder, ginger, and rosemary. Cover and bring to a boil over high heat. Reduce the heat to medium and cook, covered, until the onion is translucent, about 10 minutes, stirring occasionally.
5) Add the carrot, cover, and cook for about 10 minutes. Add the bell pepper, broccoli, cauliflower, black pepper, and salt to taste, cover, and cook until the vegetables are tender, about 10 minutes more.
6) Add the reserved squash flesh and wild rice. Use a wooden spoon to mix the stuffing together; it should be a bit creamy. If all the liquid has dried up, add about ¼ cup broth or as much as is needed to make it slightly creamy. Taste and adjust the seasoning. Remove from the heat.
7) Arrange the acorn squash shells on a baking sheet and divide the stuffing evenly among them. Sprinkle the pine nuts on top. Bake until the pine nuts are browned and the stuffing is heated through, about 20 minutes. Remove from the oven and let stand for a few minutes before serving. Serve hot.