Preheat the oven to 425°F. Neatly slice 1/2-1″ off the top of each squash and set it aside.
Check the bottoms to see if they’re level. If not, slice off enough so that the squash will stand steadily. Scoop out the seeds, rub the inside and out with olive oil, season with salt and pepper, and place the squash in an oiled baking dish.
Heat a skillet over medium heat and add 4 tablespoons of the olive oil, followed by the onion and saut? until lightly browned. Add the garlic, rice, walnuts, barberries, cherries, apricots, and rose petals. Stir well and continue cooking for 5 minutes, adding a little water if the mixture is dry. Taste and season with salt and pepper.
Fill each squash with stuffing and replace the tops. Whisk together the orange juice, saffron water, and the remaining oil and pour over the squash. Cover tightly with a dish lid and bake for 25 minutes, basting occasionally with the juice. Uncover, baste, and bake until the squash is golden and tender, about 5 minutes more. To serve, transfer the squash to a platter and pour the liquid from the baking dish on top. Garnish with rose petals.