It is highly unlikely that any member of this site plays out of a monostand of rough, or fairways, or even greens for that matter unless the course is brand new, or was completely renovated recently. Superintendents are more concerned with keeping non-grasses out of the rough, like dandelions, thistle, clover, sedges, etc. etc. than trying to keep a monostand of whatever species are considered "desirable" in rough. There is no chemical regime that will kill one grass over the other, unless you are talking about perhaps Poacure, but if you are spraying Poacure in the rough than you are Augusta National.
The course I worked at for many years had mostly bluegrass, but also rye, various fescues, poa annua, poa trivialis, in addition to dandelion, clover, sedges necrotic ring spot, etc etc. And the course was considered fairly elite. Point being, the priority is to have grass in the rough, any grass. Which particular grass is is not of particular concern, as the golfer typically doesn't care as long as it's a fairly consistent height (aka mowed at a reasonable frequency), and is not bare dirt or weeds.