Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Using a sharp knife, carefully slice each acorn squash in half from stem to tail and scoop out the seeds with a spoon.
Brush the cut sides of the squash with a little olive oil, then place them cut-side down on the prepared baking sheet. Roast in the oven until tender and caramelized around the edges, about 40-45 minutes.
While the squash roasts, prepare the filling. In a mixing bowl, combine the cooked grains, roasted vegetables, dried sage, cinnamon, and a drizzle of olive oil. Mix everything together until well blended and season with salt and pepper.
Once the squash halves are tender, remove them from the oven and let cool slightly. Then, gently flip each squash half over and scoop some of the flesh into the bowl with the filling, slightly mashing it to create a thicker mixture.
Fill each squash half with the prepared grain and vegetable mixture, pressing lightly to pack the filling in.
Return the stuffed squash halves to the baking sheet and bake uncovered for an additional 10-15 minutes, until the filling is heated through and slightly browned on top.
Remove from the oven, let cool slightly, then serve warm, garnished with fresh herbs if desired.
