Preheat the oven to 400° Fahrenheit and line a large baking sheet with parchment paper.
In a large bowl, toss the sliced acorn squash with the grapeseed oil, harissa, rose petals, and 1/2 tsp salt. Then place on the baking sheet (leaving a bit of space between the slices) and bake for 25-30 minutes, or until tender.
While the acorn squash is in the oven, make the couscous per the instructions on the package. Once it's done, add the olive oil, toss, and set to the side.
Now make the yogurt sauce. To do this, mix together the yogurt, crushed garlic, 1/2 tsp salt, 1 tsp sumac, and the juice of one lemon. Stir to combine, then set to the side.
Once each component is done, it's time to assemble. Add some couscous to 4 plates. Divide the acorn squash into 4 portions, and then place them atop the couscous. Top with the yogurt sauce and some fresh cilantro, and serve!