When Max started shipping with Arnold a few versions back it included a Rounded Corners map. https://docs.arnoldrenderer.com/display/A5AF3DSUG/Round+Corners
@ZombieWells Before you do your test make sure to upgrade MAXtoA Render Setup Dialog > Arnold Render > MaxToA Version. That rollout will tell you if an update is available. I spent a couple hours trying to work around a bug, but the latest version had already fixed it.