Trey Fox, 19, of Glenwood Springs, Colo., Christian Morgan, 18, of Aurora, Colo., and J.J. Quinlan, 19, of Everett, Wash., were injured and were taken to hospitals in Laramie, Wyo., and Loveland, Colo.
Morgan's injuries were serious but were not believed to be life-threatening, troopers said. Fox had moderate injuries.
The nature and extent of Quinlan's injuries weren't known.
Fox was driving and apparently fell asleep, investigators said. They said alcohol and drugs aren't believed to be factors.
The pickup was northbound on U.S. 287 six miles south of the Wyoming border at about 5:30 a.m. when it went off the left side of the highway, struck a rock embankment and a tree and then rolled.
University President Tom Buchanan offered condolences to Narcisse's family.
"The loss of any student saddens us immeasurably," Buchanan said in a statement. "The entire university community grieves his loss."
Coach Dave Christensen called it a "terrible tragedy, and a terrible loss." He offered his support to the players' families.
Counselors will be made available to players, coaches and other students, university spokesman Tim Harkins said.
Narcisse, a freshman, was linebacker.
Fox is a cornerback, Quinlan a linebacker, and Morgan a wide receiver. Fox and Morgan are freshmen. Quinlan is a redshirt freshman.
None of the four played in Wyoming's 28-20 victory over Southern Utah on Saturday.
Wyoming plays at No. 5 Texas next weekend. Texas coach Mack Brown issued a statement offering his school's sympathy to the Wyoming players' families and the university.
"It's such a sad day to see a life taken so early," Brown said. "Our thoughts go out to Ruben's family, and we pray for them and the families of the injured young men."
In 2001, Texas defensive end Cole Pittman was found dead at the scene of a one-car accident northeast of Austin.