Looking to bargain hunt the recent plunge in Chinese stocks—bid up in an "enormous speculative frenzy" over the past year—would be like "catching a falling knife," former Morgan Stanley Asia Chairman Stephen Roach said Tuesday, just days after returning from a trip to China. Chinese stocks were volatile again overnight, but closed well off session lows, as investors remained doubtful of the efficacy of Beijing's recent market rescue measures. "The bubble is bursting" and predicting the bottom is anyone's guess, Roach told CNBC's "Squawk Box" in an interview. He added, however, that China's efforts to transform its economy remain unchanged....