Pulse the celery, onion, carrots, thyme, sage, 1/4 teaspoon salt, and black pepper in a food processor until finely chopped.
Add the olive oil to a large skillet on the stove over medium heat.
Add the vegetables from the food processor and cook for 10-12 minutes. Remove from the stove and set aside to cool.
Preheat the oven to 425°F.
In a large bowl, mix the bread flour, baking powder, baking soda, sugar and 1/2 teaspoon salt together.
In a separate small bowl, whisk the buttermilk and 4 tablespoons melted butter together.
Add the wet mixture to the dry mixture and stir until a dough forms. Add the cooled vegetables and stir to combine.
Place 12 heaping spoonfuls of the dough on a baking stone.
Place in the oven and bake for 12 minutes.
While the biscuits are in the oven, combine the remaining 4 tablespoons melted butter, with the fresh chopped rosemary.
Remove the biscuits from the oven after 12 minutes, and brush with the topping.
Place the biscuits back into the oven for an additional 6-8 minutes.