Reduce the oven temperature to 350°F. Lightly spray a 9×9-inch baking pan with nonstick spray and line it with parchment paper, leaving some overhang for easy removal.
In a microwave-safe bowl, combine ½ cup of the chocolate chips and the oil. Microwave in 15-second intervals, stirring after each, until melted and smooth. Set aside to cool slightly.
In the bowl of a stand mixer fitted with the whisk attachment, beat the granulated sugar, brown sugar, eggs, and vanilla on high for 5 to 6 minutes, or until the mixture is pale, thick, and about doubled in volume.
With the mixer on low, slowly add the melted chocolate mixture. Mix just until combined.
In a separate bowl, whisk together the flour, cocoa powder, and salt. Add the dry ingredients to the wet ingredients and mix on low just until combined.
Fold in the remaining ¾ cup chocolate chips and about 1 cup of the roasted balsamic blackberries. Be careful not to overmix.
Spread the brownie batter evenly into the prepared pan.
Bake for 30 to 38 minutes, or until a toothpick inserted into the center comes out with moist crumbs but no wet batter. Start checking around 30 minutes, as the added fruit may increase the baking time slightly.
Immediately after removing the brownies from the oven, gently press the remaining roasted balsamic blackberries into the top.
Let the brownies cool in the pan for at least 30 to 45 minutes before cutting. For the cleanest slices, let them cool completely before serving.