
It appears that your roof has a synthetic underlayment on it, which is not uncommon beneath metal roofs these days. It has to be installed properly but most synthetic products are warranted to last from 90 - 180 days exposed to the weather. As far as the roof you select, metal comes in a huge variety of products and grades, including exposed fastener and concealed fastener. There are different grades of coatings as well. And, of course, proper installation is critical. 26 gauge is certainly a fine gauge for the type of exposed fastener panel you're considering.
The photo is too small for me to see detail. The warranty would come from the manufacturer. Is there any name printed on the underlayment? If not, you will need to look for a roll label or wrapper or ask the contractor.
How do I know if my warranty is for 90 or 180 days? We actually just passed the 90 days. Can you tell from my photo if the synthetic paper was properly installed?
I think it simply says 84 Lumber on it.