If you are reaching your inventory weight limit, wait until you are about to pick something up that would put you over the weight limit and roll as you pick it up. If done correctly, you will still be able to move at full speed, combat normally, and go well over your max weight limit. Your run animation may look really strange but I am not sure whether this is only client side or server side.
Every once in awhile it will just randomly stop working and the normal encumbered slow effect will be active until you go below the weight limit and perform the roll again (cannot do the roll while encumbered obviously).
Saves a ton of time if you aren't ready to go back to town and want to farm just that little bit more!