Using a feeler gauge how do you set the valves on a Chevy 350 with a hydrolic roller cam?

You shouldn't need feeler gauges for a hydraulic cam. Set each valve to zero backlash and preload the rocker 1/4-1/2 turn just as you would with a hydraulic flat-tappet cam. Detailed instructions can be found in any repair manual that covers small-block Chevies.