Leave 2 tablespoons of drippings in the roasting pan and place in the oven.
Combine the flour, salt, eggs, milk, and remaining 2 tablespoons of drippings in a food processor or blender and process for 30 seconds. Pour the batter into the hot roasting pan and bake until puffed and golden brown, 35 to 40 minutes. While the pudding is cooking, carve the roast. Serve the pudding with the roast.