There is not much history associated with the Rogers & Spencer. The Federal government bought a few thousand near the end of the Civil War, never issued them and sold them as surplus after the war. They were never sold on the civilian market except as government surplus.
Likewise, the Federal Government bought tons of Remington revolvers during the war but in civilian sales Colt outsold Remington by about five to one, even though Remingtons were cheaper. That continued through the breechloading era until Remington finally gave up producing handguns. One can speculate on the reasons for that but I suspect it was because of the superior handling properties of the Colt design. People in those days weren't much concerned about accuracy of carefully aimed shots from a handgun. Handguns were weapons for close range fighting and the "point and shoot" properties of the Colt were clearly superior. Today many shooters prefer the Remington for its superior sighting arrangement but groups on target from benchrest don't mean diddly squat in a gun fight.