Uni-solar is out of business so warranty is out of the question. Considering the difference in cost, pnichols could buy several, have back ups in case of a failure and still be ahead of the game.
Also I wouldn't consider them even with a warranty if they had a lot of bad reviews or reports of failure. I'm sure they are some out there but I can't remember any.
Good question on the new roof question. There may be something that will release the glue but I'd probably just cut the rolls out of the old roof and glue both to the new roof.
pnichols, I found a spec sheet on the PVL series 144w and it does have the triple-junction tech.