What stat is used in the crafting room in fallout shelter
It depends on the item being crafted. Some items require strength, some require intelligence, etc.
That said, there are no restrictions on what you can and cannot craft, based on your dwellers SPECIAL stats. What this affects is how long it will take to craft the item. For example, when crafting an item that requires intelligence, dwellers with low intelligence will take longer than those with high intelligence.