Does any have a complete list or know all the job descriptions for a game company that deals in mostly the MMOTPG market (but do small games on the side)? I was wondering if there really was a Research and Development department for a video game company what was their purpose within the company?

Technology is constantly changing and successful developers need to keep on top of these changes. They also need to keep developing new tech and tricks to get ahead of the competition. That is what R&D would do. As an example you can bet that John Carmack isn't developing engine tech for ATI X850 technology - he will have the very top of the range industrial strength video card and be developing technology to run on whatever kit ATI and Nvidia are planning to launch next year or the year after. R&D of that nature will keep them ahead of the pack.