I had a set of vortec heads machined for .600 lift, new springs installed, and screw-in studs put in. They also installed push rod guide plates. I'm not sure what roller rockers to buy. I want 1.6 ratio but don't know if i should get self-aligning ones or full roller. To my understanding, self-aligning roller rockers are only necessary if you have centerbolt valve covers and are not using push rod guide plates. Which roller rockers are recommended?

I could be wrong, as I haven't dealt with newer heads. But IIRC, if you've got guide plates installed, you can run a regular rocker arm (non self allign).

I've got a set of Harland Sharps in my 454. No issues with them. Have a set of CompCams in my K5's motor. Again no issues. As long as you stick with a name brand....you'll be fine.

For the ratio. Some cams are designed to be run with 1.5's, not saying you can't use 1.6's....just tossing that out there. Might wan't to check with your cam company for their opinion.

The need for self aligning rockers is eliminated with the guide plates. It's also important to check to see if there will be any push rod binding where the push rod passes through the cylinder head. The Vortecs use this hole and the self aligning rockers to maintain valve train geometry. With 1.6 rockers, there is a binding issue.
As far a rockers go, you can't go wrong with Comp. I use 1.6 Pro Magnums on my Vortecs.