I know this has been asked before but I just can't get the hang of dodging a dragon's breath. Everyone says that Whirlwind sprint or stealth roll should do the trick but every time I try it, the dragon is "locked on" to me and it's body actually rotats with my move, making it impossible to move out of fire. So far the only reliable way I've found is abusing LoS or bashing/unrelenting force.
Usually what I tend to do is either stay out of range of the dragons attack and hit it with spells/arrows or stay within its melee reach and strafe around it. Yes, the dragon will follow you, but if you use its size to your advantage you should do fine. IF you aren't exploring with a companion this may be a little harder to do, but with a companion you should be able to split the dragons focus.
If for some reason you are caught within range of the dragons breath but you aren't close enough to strike, using terrain to your advantage is always a viable strategy. If you don't have a companion, buying a horse can always be a worthwhile investment as well. They can/will attack the dragon as well and give you that extra distraction you may need.