On the Rhein I stayed in Boppard, in a Privatzimmer. The young couple only spoke German to me. Don't know if they speak English.
In Rothenburg I stayed at Reidel. I don't know if Rick still lists it. (He compared it to the Munsters, but my wife, who doesn't speak German, thought the owner, Lorry, who barely speaks English, was quite charming.) The place is close to the Fussgangerzone and filled with antiques, but a little rustic (bathrooms on the floor).
I was not at all impressed with Baden-Baden. I stay elsewhere in the Schwarzwald.
For Füssen, I would recommend the neighboring town of Pfronten, but, again, where I stayed, no English. I think they might speak English at Aggenstein. It seemed nice.