If roommates are smoking marijuana in a common room and I am upstairs in my private bedroom, could I be legally implicated?

Of course there is risk. If the police sweep in,they arrest everyone and leave it to you and your lawyers to sort it out. They will press one roommate to rat out another, etc. Two ways to eliminate risk: Move, or get the pot out of the house.

Yes there is a legal risk. Frequently in drug arrests inside an apartment or house, the police will arrest everyone found in the residence, regardless of where you are in relation to the drugs or paraphenalia. However, in order to search a residence, the police must either have a warrant to search, or probable cause to enter. Another attorney responded that you should move or get the pot out of the house. Do you trust your roommates enough to remove the drugs if asked? Best just to find a new apartment.

short answer is YES. If the police come in they will likely arrest everyone within the place and arrest all for possession based on a theory of constructive possession.