I'm sorry but Poconos is wrong about how solar on a roof top works. While it is true that the system is "closed" when it is running, so the actual effect on the pump is small, all modern roof top solar systems are "drain back" type. That is, when the system is OFF, the water in the panels is allowed to drain back into the pool (through the returns on the return side and through a small hole drilled in the valve on the pressure side. They used to make "non-sealing" valves, but now they just drill a hole in the valve ball.). The water does NOT stay in the system when it is not running, a vacuum breaker is installed near the top of the system to allow air into the system so the weight of the water doesn't collapse the panels. Thus, your pump DOES have to get the water up to the solar panels everytime it turns on. I researched this for months and months before going solar, every major manufacturer designs this way, although it is not always clear on their web sites.

For a 3 story roof, you may have to (or want to for efficiency) go to an auxiluary pump. My panels are about 24 feet above pool level and they work fine with a 2HP pump (I am investigating if I can go smaller). For your size pool and only wanting a 5 degree or so rise, you might consider one of the smaller systems that simply tie into your filter lines (these are "closed" as Poconos said). I have a friend that has a one 4x20 panel that he uses for just such a purpose, it is laid out on a rack right next to his pool.