I also have Rox risers. As you've seemingly just experienced, they can get cocked off a bit, which is both a feature and a bug.
It's a feature, in that they allow some flexibility in the bars-to-steering head connection. When I ate dirt road last fall, my handlebars were knocked askew but nothing permanently bent, which is kind of a miracle. But I had to realign my Rox's.
It's a bug, in that the Rox risers rely solely on clamping force to resist rotation, so are slightly prone to becoming misaligned now and then.
Overall though, I'm a fan. They're ridiculously well-made, beautiful, solid chunks of aluminum, and there's nothing else quite like them.