Nope. Misprision of felony requires a felony in the first place, and six months ago, there wasn't one.
But, anybody who knows a dope smoker (and I'm NOT looking at you, DiogenesLamp) who also possess a firearm, that hasn't turned the felon in to some judge or other person in civil or military authority under the United States, has committed misprision of felony (18 USC 4), the underlying firearm possession felony being 18 USC 922(g).
Thanks for the clarification. It still sounds as though the roommate may have made a mess for himself if the authorities want to get vengeful, which I expect they might.