The SA seems to disappear from history books after the Night of the Long Knives, yet really only it's leadership was killed, and it technically still existed as an organisation. What was its continuing role, and why was it kept in existence? How large or powerful an organisation was it?
After this event the SA (Paramilitary wing of the Nazi party) was consolidated with the SS and the leadership was murdered. The point of this purge was to concentrate power with those that shared the same vision with and were loyal to Adolf Hitler and Heinrich Himmler. So, anyone that was a threat was 'removed' quickly and violently because if anyone escaped with support then they would have had to spend time jockying for power within their own party which would have given the other parties and freikorps time to manuever against the Nazi's now obvious grab for absolute power over the country.
After the Night of the Long Knives, the now super downsized SA was basically used recklessly by the Nazi's since they no longer held much meaning. Basically, they were used for the dirty work during the 30's that the other Nazi's couldn't be bothered with doing. By the time the war broke out, most of the SA men were drafted into the Wehrmacht and sent off to one of the fronts. Remember, membership into the SS until late in the war was restricted to "perfect Aryan specimens" so the stormtroopers of the SA couldn't exactly just switch over after they were out of a job. They were run very differently as organizations.
The Rise and Fall of the Third Reich - William Shirer