The camera is no different to normal camera , without zoom .
So 50 yds away its difficult to recognise a face ,no different if you were to photograph someone at 50 yds
DJI Phantom , so easy to fly ,tons of youtube video , 4K resolution and 100% no wobble with the camera in the air , auto take off and land , fuly GPS controlled , Absolutely amazing .
Hours of fun and bitten fingernails ahead. Have fun. Could I suggest you take a look at Litchi software. It allows you to pre-program a route and take photos exactly where you want to. (although I have not kept up with DJI developments) It could be useful for your roofing excersise where you do not want to miss a shot.
One other hopefully helpful suggestion - take a spotter with you especially early days. There's so much info coming at you it is easy to lose track of the drone.