I managed to do LBH, Rosebud, Fetterman, Wagon Box, Phil Kearney, and Fort Laramie. Also Fort Bridger but that wasn't a military fort, just a way stop on the pilgrim trail from east to west. And did the Cody museum which you should include if you are in the area and have the time - vast array of weapons on display but much of native culture as well. This was all in one trip. Oh, and the fort near Custer, South Dakota which I think was part of the Black Hills gold hunting days. Did lots more but that was the history portion of the trip. Epic vacation for me.
Like others, there was no one at Rosebud so all I did was roam about a bit - specially noted the buffalo jump and surprised at how low it actually was. Stop was short as we were on our way to LBH where we spent the bulk of the day.