This is a lousy answer, but you can find it in Artlicle 234 of the National Electrical Safety code, but you have to know your cable type, wind load, etc to calculate.
Article 110 and 490 of the NEC do not really address any specifics of 4,160. OSHA is very concerned where there is access to the roof. Will there be equipment requiring service up there? If so, I suggest the minimum is 10 feet which is the minimum clearance for working unless trained, and properly PPE'd.
Hope this gives you an idea where to start.
