I do a lot or roofing; I have done a lot of quality compliance inspections for different companies. I am in S. Texas, which has the same high UV days as well as high heat and humidity.
I am also familiar with a lot of different coatings and applications that "extend" the life of the roof.
In a word, baloney. In two words, no way.
ANY clear coating of any kind that you expose to that kind of punishment (18 hours of sun and heat a day) will fail. Polymers are either resins or plastics, and they will sit on top of the roofing material. You will never get the roofing material clean enough to provide any kind of seal at the time of application. Even if it appears to penetrate at some demo, it is probably just the carrier or solvent going into the surface.
More bad news. All the roofing products we use around here (excluding tile and metal) use petroleum products in their manufacture. They off gas vapors for years, until they are dried out and crispy. So, you will have petroleum vapors off gassing under your plastic finish. Think of the coating as an instant green house.
And when it starts to fail, water will seep in under your poly film and begin to mold and mildew. Then the finish will start to flake off. Think of a varnish covered front door that hasn't had any finish applied in many years.
But then, they may try to sell you a renewal material for future application. That makes it even worse. All poly finishes are film finishes and will not "renew".
You BEST bet is to have your roof installed correctly, and if you are in doubt about them blowing off have the roofers put a couple of extra nails per shingle, and make sure the nails are in the 1 /14" range when the roof is installed. Sometimes a shot of mastic will help ridges and hips in addition to the nailing required.
Robert