Of course he has a chance to win 25-30, but SO much can happen over the course of a season, even for a healthy pitcher. It is highly unlikely that anyone will win 25-30 this year. Here is the win total for the MLB leader in wins over the last 10 years (notice that NO ONE has gotten to 25 wins in that time):
2005 - 22 (Willis, Florida)
2004 - 21 (Schilling, Boston)
2003 - 22 (Halladay, Toronto)
2002 - 24 (Johnson, Arizona)
2001 - 22 (Morris, Co-ards)
2000 - 22 (Glavine, Atlanta)
1999 - 23 (Martinez, Boston)
1998 - 20 (by 4 different pitchers)
1997 - 21 (Clemens, Toronto)
1996 - 24 (Smoltz, Atlanta)
The last time any pitcher won as many as 25 games in a season was in 1990, when the A's Bob Welch won 27. The last time before that was Steve Stone for Baltimore in 1980. That's only 2 25-game winners in the last 26 years. The last NL pitcher to win that many was Steve Carlton with 27 in 1972, and that was before relief pitching became as big a part of the game as it is now. That should tell you how difficult it is to win that many games in a season, even with good health and good offense and defense behind you.
So, yes, Roy has a chance to win 25-30, but not a realistic chance. 20-22 is probably the most realistic best-case scenario, but that's only if everything goes right, meaning no more games like last night.