A tip: Rox risers come with low-grade, A60-2 stainless screws. The thread forms on those tend to be smaller, so they have less engagement with the female threads, and they are rounder and much softer. As a result, they are likely to wear themselves and the engaging threads faster and make both unserviceable in many fewer adjustment/maintenance cycles. In addition, the stainless can cause bimetallic corrosion with the aluminum. On the non-anodized clamps, you'll start to see the white crust of Al oxide if you take one out after just a few wash cycles.
I replaced them with Metric Zinc-Coated Class 12.9 Alloy Steel screws from McMaster-Carr
. It's been a long time since I reviewed the spec charts, but off the top of my head, I believe they are at least twice as strong before yield, and have better thread forms and the best type of anti-corrosion coating there is for hardware.