Cohn held offers from nearly 20 schools, including Bradley, Central Michigan, St. Louis, Santa Clara and Southern Illinois, before deciding on the Rams.
"Coach Eustachy and (assistant Niko) Medved did a great job," Cohn's AAU coach Mike Mullins told ESPN Chicago. "David's an explosive scorer, athletic and gritty defender. His best days are ahead of him as he gains strength to match his skills and athletic ability."
Cohn joins Paris Junior College (Texas) power forward Marcus Holt as 2013 Colorado State commitments.