Hi there,
I am currently a Cdt Cpl and am hopefully working towards a promotion to Cdt Sgt soon, so I would like some advice on the roles of a SNCO compared to those of a JNCO. What is the main difference between the two and and what is expected of a SNCO which is not of a JNCO?
Thanks in advance
The main difference is the primary tool you have at your disposal to undertake any task. As a corporal you have cadets, as a SNCO, you have Corporals. You have to take a step back and start to manage other managers, without micro-managing them, whilst also inspiring them as a leader.
As @Baldrick has said.
SNCOs focus more on management of JNCOs and cadets. SNCOs are expected to teach drill etc. You are also expected to plan to implement squadron policies and goals. Bottom line is that you have more responsibility and therefore this requires more work.
For example as a cadet flight sergeant (not that long ago) 
I regularly instructed cadets in academic subjects. Junior cadet training was entirely my responsibility, both academically and with regards to drill & discipline.
In addition to what has been said - think of what you currently do as a Cpl. I imagine it’s very much be told what needs done and you get cadets to do it. As a Sgt that may be the same however you will be expected to know what needs done and get it done. You are responsible for more people and jobs than you are as a Cpl. On camps you may also be given responsibilities such as flight IC/2IC and you will be expected to be a role model (even more so than presently).
look at your own location.
What do the Sgts do on your Squadron that you don’t?
We is written above is correct, but the best guidance is what goes on in your own Bubble. A Sgt on one Squadron will differ to the next Squadron 10 miles down the road so consider what your Sgts are doing, what experience have they got (camps, courses, PTS badges, qualifications) they have you don’t.
Some COs go on who they trust, maturity and length of service, others have a stricter tick box of having completed X camps, Y courses and have Z years experience so I would say consider all of what has been suggested and compare that to your Sgts and see what your missing.