Foster is among the five wide receivers that made Seattle's initial 53-man roster, John Boyle of the team's official site reports.
Foster earned his roster spot with a strong training camp that carried over into a productive preseason, which included a touchdown catch in Seattle's first preseason game. The 25-year-old wide receiver finished the previous season on Seattle's practice squad but has yet to appear in a regular-season game. Foster will likely be limited to a depth role barring injuries to Jaxon Smith-Njigba, Rashid Shaheed, Cooper Kupp or Tory Horton (undisclosed), the last of whom isn't believed to have a long-term injury.