I've built several SB non stroker motors using the standard 590 Mopar lift cam with great HP results. Do I use the same cam specs if I use a roller cam?

I've done that before. They have to change the lobe profile itself but they can give you the same specs.

...but if you do that, are you really taking advantage of what the roller lobe design gives?

Or are you saying: grind me a lobe with this much duration at 0.050" (to simplify) AND of course grab as much extra duration & lift at all the other places in comparison to what the non-roller lobe had?

I assume what they did was make a roller cam with that lift and duration.

I'm looking to see if the roller , because of its faster ramp, needs a different spec? I guess I'm looking to find out if the roller will make more power with a similar cam profile.

I very much doubt you'll find a solid roller camshaft that will have the same seat timing and lobe lift. I'd expect the solid roller to have more lobe lift.

What specs are you referring too? Adv duration, 0.050 duration, 0.200 duration and max lift?

If all those Specs are the same between the two cams, the lobes will not be faster, and the power will be the same.