One way you could do this is by using baseball-reference.com's list of starters, year-by-year. Here's the link for the Red Sox as an example:
Boston Red Sox Positional Chart - Baseball-Reference.com
As a Red Sox fan, here's my 25-man roster from 1980s Boston:
C - Rich Gedman
1B - Bill Buckner
2B - Marty Barrett
3B - Wade Boggs
SS - Glenn Hoffman
OF - Jim Rice
OF - Dwight Evans
OF - Rick Miller
DH - Carl Yastrzemski
Off the bench (5 players):
C - Gary Allenson
3B - Carney Lansford
SS - Jackie Gutierrez
OF - Mike Greenwell
OF - Ellis Burks
Starting rotation:
1. Roger Clemens
2. Bruce Hurst
3. Oil Can Boyd
4. Al Nipper
5. Bobby Ojeda
Bullpen (6 pitchers):
Bob Stanley
Luis Aponte
Dennis Eckersley (6th starter, long relief)
Joe Sambito
Mark Clear (barely makes the cut)
Tom Bolton (only makes cut to give a 2nd lefty out of weak bullpen)