Would we really say it took 3-4 years? Obviously he split time with Hayward, but that didn’t seem terribly uncommon for the late 80s when many teams employed a more balanced two-Goaltender system.
The most-worked goaltenders between 1985-86 and 1988-89 (John Vanbiesbrouck, Grant Fuhr, and Tom Barrasso) averaged just 54-56 games. Compare this to just 10 years later (1995-96 through 1998-99), when the three most-worked goaltenders averaged 65-71 games.
Vanbiesbrouck actually played more games from 1996-1999 (ranked 9th) than he did from 1986-1989 (ranked 1st).
Roy was one of just four goaltenders to reach 100 Wins over the 1986-1989 frame. Earned a shot at a regular spot by winning the Calder Cup in his draft year, won the Stanley Cup while being the youngest Conn Smythe winner as a rookie, split the Jennings the year after, took a 2nd Team selection in Year Three, and the Vezina and a second Finals run in Year Four.
Not too many hotter starts through the early-20s than that. Sawchuk, Lumley, and who else?