Well, to clarify a bit, it really depends, at the outset, whether you're looking at buyside or sellside (to a degree). For now, lets deal with sellside.
If you are a sales trader, your role is both the trader as well as the salesman, in that you are attempting to sell your firm's research or other products to a client, in an effort to generate trades. You then are responsible for the execution and monitoring of those trades, meant to pay you for your efforts in providing the products.
If you are a trader, you are, in most cases, the person who inputs those trades into the system, and directs them to whichever place they need to go to be executed (such as the floor). You then relay back to the sales trader the updates and changes necessary/requested to make sure the sales trader is fully aware of the trade's status at all time.