Jim Rooker was born September 23, 1942 in Lakeview, Oregon but grew up in the Denver area and graduated from Cherry Creek High School in 1960. He was an outfielder in high school but after signing as a free agent with the Detroit Tigers, he was converted to a pitcher. He worked his way through the Tigers farm system with stops in various places in Americana such as Jamestown, Duluth, Montgomery, Rocky Mount and Toledo.
He excelled for Toledo in 1968, going 14-8 with a 2.61 ERA. The Tigers, who were in the midst of a World Series winning season, called up Rooker in mid-season.