first the link between sky and air to the hub is radio (9xx mhz in the US I think and 8xx mhz in Europe for most) and not wifi and works pretty well over distance when open field (hence not walls like I have that are 50 cm thick 
) The hub uses wifi to link to your internal network, internet box
Roof is a good spot as long you can fix it solid via a pole with or without stabilisation wires. Sky is pretty sensitive to large swing (though algorithms clean that mostly out, but less it has to filter, the better)
Also observe your garden, we have some testers with nasty little birds using the sky as a landing pad 
… if you have those little birdies 
using your roof as observation platform … that might also become a problem …
As you can see testers and the Weatherflow team have already had fun with many factors that influence the sky unit (vibration, obstruction of light measuring etc …) 
