Jack Casady with Rotosounds?

Well, since no one else answered, I'll give it a go. Sure, I've used Rotosound Swing 66 stings on my Jack Casady bass . I did this because the DM , medium light stings became unreliable after the owner sold the company, and some one else was making them under their name. I would have stuck with the original Blue steel string, if not for that.
Rotosounds are great, of course, they are a bit heavier feeling and a little more body to the sound of them. A very good sound on that instrument, though you'll probably have to do a little bit of set up changes due to the higher tension. The JC bass is very responsive to the type of string you put on it. I've had Rotosounds, Dean Markleys, Thomatik-Infeld Jazz flats. All bring their own characteristics to this instrument.
As I understand it, some of the original Dean Markely technicians got together and are making their strings as they were intended to be made under the Apex brand. Try: Apex-string.com. I believe they do direct sales, and you can get the cryogenic stainless steel strings made properly, again.