I haven't had the need to push a Ruger rear sight with a sight pusher. At least any of the rear sights.
I think many of the tool makers of sight pushers don't offer them for round receivers due to the many varied sizes of the receivers. It's easy to find a pusher for "flat" surfaces.
I'll have to check my pusher to see if it can do round receivers. Been a while since I had mine out.