Johnson was previously committed to Louisville.
Warren was also named Big Ten Offensive Player of the Week and AP Player of the Week for his performance against the Trojans.
Barker became the first Nittany Lion to hit four field goals in a game since Tyler Davis in 2016.
The Nittany Lions last faced Wisconsin in a season-opening win in 2021.
Warren's performance against the Trojans was record-breaking.
It was a down week for many former Penn State football players.