Oh I pretty much got the Medvedev part. Again, I had equal difficulty winking at it.The Medvedev part was sarcasm. I know, it doesn't translate well to text.
The things with Roddick is he was the prototypical Serve +1 player. That doesn't work as well on fast grass, where you really need to close and take the ball in the air.
As far as Serve +1, that's pretty much exactly it. That's more concise than my paragraph.
Young ("peak") Fed, while largely unproven on faster grass (or anything) because of conditions in his era, at least has the full array of skills that basically no one else in his or subsequent generations have had - the complete all-court player. He's not exactly Sampras and Agassi put together, but he's probably the closest thing that we'll ever see to that. It's not unreasonable to think he'd do well on faster grass. I'm not putting a number on it, but I don't think it's out of the realm of possibility that he wins a few more than he did IRL.
It's hard to know how Nadal and Djokovic would fare, as their games are fairly ideal for the modern slower conditions - esp Djokovic (Clay is Clay for Rafa). This is speculation, but one thing that we've observed from them over their long careers, is that they have continued to evolve, tweak, and improve aspects of their game as they go - something that we don't usually see from many other players, frankly. It's contributed to their longevity and success. Being ATG's that they are, I'd imagine they'd do that when confronted with faster courts and faster grass at Wimbledon - at least over time. I'm skeptical that Novak would be quite as successful, but I wouldn't be surprised if they each got at least 1-2 Wimbledons, regardless of fast courts. I think the 2007-10 Rafa form plays pretty well, regardless - maybe he only wins 1, but still, it's hard to imagine that Rafa getting shut out.