Down 21-13 late in the fourth quarter, Davidson (0-4) was threatening on a drive starting from its own 1. Sparked by a 29-yard rush by Spencer Perry and a 47-yard pass from Jonathan Carkhuff to Tim Hines, the Wildcats got to the Blue Hose 14.
Carkhuff was sacked, then picked off by Williams, who ran 76 yards to the 6. Rouse scored one play later with 2:53 remaining.
Carkuff, who threw for two touchdowns, was intercepted earlier by LJ Perry, who ran 66 yards for a 7-0 score.
Rouse started the run of 21 unanswered points for Presbyterian (2-3), capping an 85-yard drive with a 3-yard TD late in the third.
Cedric Byrd's 44-yard punt return to the Davidson 19 set up the Blue Hose's next touchdown.
ESPN college football Insider Joe Schad discusses the latest regarding Les Miles' job security at LSU.
Iowa-Nebraska Postgame Breakdown
Jordan Canzeri's long touchdown runs on two consecutive drives spurred No. 4 Iowa to a win at Nebraska that sent the Hawkeyes to their first unbeaten season in 93 years.
Adam Mitcheson 23 yd FG GOOD
The Hawkeyes pulled away in chilly Lincoln to roll into the Big Ten title game with a spot in the College Football Playoff in their sights.
Iowa coach Kirk Ferentz describes his team's 28-20 victory over Nebraska and says he is pleased with his team's undefeated record, the first 12-win season in Iowa history.