How to pass CCIE in one sitting?
That depends on how much you learn, exposure/experience in the subjects that will come out in the exam, also how much you covered when preparing for exam. Check the CCIE blueprint for both Written and Lab exam for the CCIE path that you're interested.
What will be your role?
That depends on the organization you join. You might be in the pre-sales, solutioning, design, etc..
