I don't think it's necessary to use both Premiere and After Effects, since both will output the same type of file. On the other hand, perhaps you need effects that only Premiere can do?

First you will need to know your target screen resolution. I'm only producing HD so I don't remember if NTSC / PAL is an issue for regional DVD production but I do know that the pixel aspect ratio is 0.9. This is a short hand explanation; let me know if you need more detail.

In North America, you would set your Poser render dimensions to at least 720x486. The extra six pixels are "compressed" by the 0.9 pixel aspect ratio. You would render out a series of still images and import them into After Effects using the DVD preset, depending on which region you live in. Combine your passes and add effects to taste and export an uncompressed AVI, which you can load into Roxio. 

[edit] the instructions above are for "full frame" and I just realized that you said "widescreen". Not much difference.

First, you'd need to know your target frame aspect ratio (the example above is 4:3, which fits standard definition CRT TVs and monitors). This is different from the pixel aspect ratio. Some common widescreen aspect ratios are: 1.6, 1.778 and 2.35, though there are several others.

I work in 1.778 for HD content, so I will use it for an example. In Poser you would set your Render Dimensions to 720x405, but your After Effects setting would remain the same as listed above. Upon import, vertically center your image sequence in the workspace. This will produce a letterbox on a 4:3 screen; it should be full frame on a 1.778 screen)

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