Riley clocked 10.02 seconds, .17 faster than the personal best he ran at the West preliminaries.
He finished second in his heat to Harry Adams of Auburn (9.96) to make the final. They had the two fastest times in the semis.
Earlier, Riley -- a hurdles specialist -- ran a leg on the Illini sprint relay that qualified for the final.
It will be the first NCAA final in the flat 100 for Riley, hurdles champion in 2010 and runner-up last year.
Jeneva McCall of Southern Illinois, the 2010 discus champion, finished 10th in that event Wednesday.
In the men's 10,000, Chris Derrick of Naperville failed in his final attempt at the NCAA title that has eluded him in four years at Stanford.
Derrick, four times a runner-up in track and cross-country championships, took third Wednesday night.
After pushing the pace and moving into the lead with 2 1/2 laps to go, Derrick could not respond to the surge Cameron Levins of Southern Utah made at the bell.
Levins, a Canadian, gave his school its first NCAA title in a time of 28 minutes, 7.14 seconds. Stephen Sambu of Arizona was second in 28:09;52, with Derrick clocking 28:17:28.