1. Forget the
Nano+. Is not stable and you will have a low quality on such work. Keep Nano for other things....personal things.
2. Any video/photo of roof need at least 2 parts...One part is intro-presentation, second part is close-ups in video and photo.
I advice you to start with a Large Circle to see the whole building and surroundings, make a big circle with the building in middle, then at end of circle (you will use for circle OBRIT MODE) go with the video straight to building.
Next, start a close-up with a close circle around roof...then get on top of roof, using 45 degrees angle, slow motion...Next, make a pass-over roof with gimbal at 90 degrees, looking straight to roof. In some points stop the drone and make best quality pictures...this pictures you will insert in video, zooming each part of picture in order to see each part of roof....
If you see problems, make close-ups.
3. Use a mapping program...there are several, a few free. Use your Mission mode and map the roof. Make a GeoTIFF file, give to client with the free program to see GeoTiff's and make measures inside GeoTIFF, will appreciate it a lot to have this tool from you. Also the engineers that will make the repair can use it for making offers and checking the damage.
4. Use editing software like free Resolve or paid Premiere...If you think you can edit this in some cheap and simple software, you are wrong.
I cannot advise you about a special angle of gimbal or speed, there is no such thing, you must adapt your footage based on building and surroundings...and be careful at surroundings, talk with the neighbors and if they are not friendly, use a blur tool to cover their property or you will have issues.
Talk with the owner...explain to him the moves and result, see if it needs some more or less.
And not as last thing...Appreciate your work properly...Remember that one branch from tree, one wire, one bird, can be fatal for your drone and you loose 2000 USD for a footage that can value....HOW MUCH NEEDS TO BE VALUED FOR THIS RISK??? That is the question that YOU need to answer yourself.
As a sample, I don't take any order anymore that is under 500 USD...Does not worth it...after taxes, risk of drone failure, insurance paid, and so on, this minimum amount is providing me confort to cover some losses from time to time, without taking money from pocket...and I can tell you that in 2 years you will change at least 1 drone if you have weekly works, no matter how careful you are.