I know she trains with the Diaz bro's, so she probably indulges here and there. Who knows though, she's a pretty serious competitor I don't think she'd risk losing her title over testing positive for cannabis.
This chick who just won gold in Judo this year mentioned something about weed after a fan commented on a possible MMA career alongside Rousey, she said something like "weed is for losers" (after Rousey congratulated her on the gold), to be clear though, she wasn't commenting on what Ronda said, she was commenting on a question a fan asked her. If she does try to compete in MMA, and goes down to Ronda's weight, we'll see how much "weed is for losers"... (as if Phelps wasn't enough for fucks sake..)