The Falcons placed Roberts (knee) on injured reserve Friday, Terrin Waack of the team's official site reports.
Roberts suffered an ankle injury in this past Sunday's loss to Indianapolis, and the issue is serious enough to cause him to sit out at least the next four games. Roberts had been working in a rotational role prior to getting hurt, notching between a 30 percent and 43 percent defensive snap share each of the previous four weeks. Atlanta signed defensive lineman Kentavius Street to the active roster to take Roberts' place in a corresponding move.