Tanguay has not played since a 4-1 win against the Montreal Canadiens on Nov. 2. He left the ice in the second period of that game after falling into the boards following a collision with Montreal defenseman P.K. Subban.
"He's out indefinitely for us right now," Roy said following practice Saturday. "It's hard to pinpoint when he's going to come back."
The Quebec native was scheduled to have an MRI exam on his knee two weeks ago but Roy did not reveal any details about the injury.
In 12 games this season, Tanguay has three goals and nine points.