He does a rookie symposium type of thing... gets them all in together... brings their families in so that they see the facility and know where their sons are working and understand what their jobs entail...
He brings people in to talk with them about what it means to be a pro (moreso than the NFL does, I mean).
Then they all sign on the same day.
Not sure exactly how it works this year, but I know I don't sweat it anymore when they say on NFL Network, "The Rams are the only team to have signed none of their players, yet..." because they do it all on the same day as part of a tradition. Signing day.