I never did anything, once I found out what the problem was, other than the occasional baby aspirin. This dog lived into old age, and I put him down when he went blind and it was plain he was miserable. And I'm NOT talking about his knees, he had just gotten old and frail and was at the end of his road. The vet agreed; she said, "He's tired, he's just worn out", he'd gone gray on his muzzle. Old dog, like 15 or so.
Roscoe will adjust, will figure out what really can or can't be done well any longer. They don't have the same reaction that we do, they just accept it and go on. (I had a kitten who was partly paralyzed, and he never slowed down either, but he could not jump & he figured that out pretty quickly after a few tries. He scrambled up and down everywhere, even a tree.) You might consider a ramp like chickens have, with "frets" so it's not just some smooth slope.
Personally, if surgery isn't going to *fix* something, it's just a huge expense and trauma, IMHO. I'd watch and wait and just see how things settle. You have the diagnosis and you can always change your mind about treatments. But that's just me. And I've not seen Roscoe, you have.
Squirrel away $1000 in a Surgery Fund and go from there.
I hope things will work out well for you both, it is upsetting when they're not 100%.