The Giants signed Johnson to the active roster on Tuesday, Adam Schefter of ESPN reports.
Johnson spent time with New York throughout the offseason and earned an initial spot on the team's practice squad, though he was cut on Friday. After the Giants' loss to the Vikings in Week 1, though, it looks like the team is exploring some schematic changes that could make an experienced fullback valuable. That could foreshadow the running game being leaned on versus Washington on the road on Sunday.