You can do both - having solar panels over a reflective white roof (like the fancy newly discovered passive radiative cooling paints) helps increase PV output by cooling the panel.

The solar panels will still absorb and radiate heat back so you won't get as much cooling as you would have just with passive radiative cooling paint, but it'd be better than just solar on a regular roof in both ways (solar output and thermally).

Thermal radiation is just EM waves, which you can reflect.

So just put the PV panels on top, and a reflective layer below.