Is it possible to save a still(jpeg) in the original resoltuion? For instance, Im doing some green screen still photos, and I import them into vegas they are originally 3072X2068. When i save them from the preview window they end up being 654x480.
No, you cannot save from the preview window at a resolution that is higher than your project resolution, and you need to switch the preview quality to "Best" in order to get that (the icon above the preview window is where you change the preview quality).
However, if you temporarily change the project resolution to 3072x2068, and set the preview quality to Best, you will be able to capture at that resolution (I just tried it, and it works).