Ollison was elevated from Atlanta's practice squad as a COVID-19 replacement for Josh Andrews on Thursday, Tori McElhaney of the Falcons' official site reports.
Whether Ollison suits up for Thursday's game against the Patriots will likely depend on the status of Cordarrelle Patterson (ankle), who is viewed as a game-time decision. Even if Patterson sits, Ollison's role would likely be limited with Mike Davis and Wayne Gallman both ahead of him on the running back depth chart.