In a statement, Roberson thanked his coaches for "taking a chance" on him and said he'll look for a new home with three years of eligibility remaining.
Diaz has led successful defenses at Texas, Middle Tennessee, and Miami.
Diaz has 24 years of collegiate coaching experience and was most recently Miami's head coach.
"I could not pass up the chance to be with this family and play the game I love again."
A little over two weeks after entering the transfer portal, the former Nittany Lion safety is joining a team in need of defensive talent.
The fall finale of Podward State features an in-depth discussion with seasoned football writer Mike Poorman.