Last fall we installed an interesting system I had not used.  Tapered
insulation, modified torch down, Pave L paver pedestals and two inch blue
stone (16" squares).  The blue stone rests on the pavers and was spaced
about 1/8 of an inch with joints open.  The pedestals are engineered to be
adjustable for whatever pitch you specify.  Very time consuming first time
installation and can't imagine increasing speed much with experience.
Best,
Leland