Yep... perhaps even higher than Rosewall, though it's less baffling a case.
Clearly, Gonzales had the big game, talent, skills and finesse to chop through Rosewall and Laver plenty of times well past his prime period of playing. One does wonder what would have happened if all their primes coincided, because I can't help but think that Gonzales might overwhelm both of them with his amazing serve and powerfully accurate game. Rosewall and Laver was an era of the little men. Not taking anything away from them but I find it hard to imagine in my mine Laver having a winning record over Sampras on grass, for example. I'd favour Sampras over Laver or Borg at Wimbledon.
I would need to see the matches really that Gonzales had against Rosewall and Laver well into his 30s and also matches from his pomp.
Gonzales led the series against Laver 3-2 in 1970? I wonder how reliable that info is. If that's true, well that's incredibly impressive.
http://en.wikipedia.org/wiki/Gonzales–Laver_rivalry
"Kramer sees as evidence of Gonzales's superiority over Laver the fact that Gonzales defeated Laver in a U.S.$10,000 winner-take-all, five-set match before 15,000 spectators in New York City's Madison Square Garden in January 1970, when Gonzales was 41 years old and Laver was still considered the World No. 1 player."
Would love to see that match.