I am finishing my garage and want to rough-in for solar photovoltaic. How much electrical, conduits would I need to run into the attic, for possible panels on the roof? In the unlikely event I want solar thermal, what would I have to rough-in?

Since there are different ways to do this, untill I had a plan for specific equipment I was planning on installing, I don't know that I would "rough-in" any conduit... I would just leave a space for it in the garage, and an easily accesible chase/pathway for conduit to the estimated roof location, untill you decide on the specifics. This is what I did on my new house plan. I left a 12" X 60" chase right in the middle of the floorplan(over garage and utility room) that connects daylight basement to attic space. Room for vent ducts, hot water pipes or electrical conduits to be added at a later date...

for PV panels a 1" conduit should be enough.

You only need to run the 3 wires from the combiner to the Inverter usually by the service panel