The New England Patriots announced today that they have signed four rookie free agents: RB Terrell Jennings, G Ryan Johnson, LB Jay Person and Australian DE Jotham Russell. The Patriots will receive a roster exemption for Russell as an International Pathway Program player. All four players attended the Patriots rookie mini-camp this past weekend. In a corresponding move, the Patriots released veteran running back Ke’Shawn Vaughn. Terrell Jennings, 23, played…