The Vikings announced the move Saturday, two days after they cut Simpson after learning of another arrest this summer. The roster decision left the Vikings thin at receiver, and coach Mike Zimmer hinted Friday that they were in the market to address depth at the position.
Johnson is in his second season out of Grand Valley State. He has experience with the Vikings' offense after playing for offensive coordinator Norv Turner and quarterbacks coach Scott Turner when the father-son tandem was in Cleveland last season.
Johnson has yet to appear in an NFL game.