Dear,
Please find below response against your queries;
How to do construction with that material?
If its matter of single room only at roof top, it means all side walls and roof will be fully exposed to all sort of harsh (hot/cold) weather conditions. You can provide insulation sheet in walls for this , 9" wall, then 1.5" insulation sheet then 4" wall at outer side. Similarly w.r.t roof, use insulated tile or heat proof foam.
What is the maximum degree difference it will make in Internal temperature throughout the Year?
Total temp difference will after this will be 10-15 degree (under harsh conditions, at optimal weather difference will be less) as compared to outside temperature.
How much long lasting it would be?
Depends upon structure care and coverage methods. If good work done, then even 10-15 Years will not effect it.
Thanks.