I think that's where i'm making the mistake! When I see him about to swing I try to roll away as far as possible from him but he always hits me. Will try your tactic when i'm back home in the evening.
P/S My 7950 is really struggling at the lowest settings for this game. Need to get a new GPU!
As a little bit of advice, when rolling to dodge boss attacks you primarily want to be rolling towards the boss as opposed to away. I've had the most success with rolling at a diagonal towards them, time it right and you're right behind the boss to get some attacks in after his swing.