Roof flashing is a crucial material every roof needs because it directs moisture away. Flashing replacement costs $200 to $500 per project area. Project areas are like valleys in the structure and features like chimneys and skylights. When you replace your roofing, you'll want to replace the valley flashing and any cracked or rusted materials. If you’re unsure about replacing your flashing, hiring a local roof inspector is around $125 to $325 for roof inspection costs.