I get your point and agree. But profession boxers with years of experiance cant roll as well as Floyd, let alone an MMA fighter. FMJ's been boxing since what, he was 5 years old? But it could be used Im MMA, it's the ***** of combat sports is my point. Not agruing it could be done as well as a pro boxer
Shoulder roll could be effective. However it does leave you quite open to takedowns compared to other positions. If the guys intent is to throw a shot then go for the TD straight after a la GSP then the shoulder roll type of defence wouldn't work great.