Robertson has been added as a cautionary measure as he was recently with the AHL's Toronto Marlies, which were shut down earlier on Wednesday due to a positive COVID-19 test.
Grubauer was added after the Avalanche cancelled practice on Wednesday following a positive test. Colorado is scheduled to play in St. Louis on Wednesday night.
Additionally, nine Vancouver Canucks players were removed from the list as the team continues to recover from an outbreak that began earlier this month. Seven members of the Canucks remain on the list as of Wednesday.
The Canucks are scheduled to return to the ice for their first game since March 24 on Friday against the Edmonton Oilers.