It's any public maps API (google, microsoft, openstreet...) that returns the height of the roof for certain points?
Imagine: you request some address and the API returns the coordinates, some information and the height of the building, if available.
OpenStreetMap has a height tag and various other building related tags like building:levels from which you could estimate the height. However note that currently most buildings lack those tags as they aren't widely in use so far. Still you could give it a try and request all buildings around a specific point or area using Overpass API / overpass turbo and then look for those tags.