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.
After being through it and seeing the other [outdoor] games on TV, just the atmosphere is spectacular. To stand here -- and we are essentially almost on the blue line -- and look up [into the stands] and knowing it is going to be packed and playing our biggest rival in this setting is going to be pretty special.
— Bruins president Cam Neely on the 2016 Bridgestone NHL Winter Classic between Boston and Montreal at Gillette Stadium on
Jan. 1, 2016