Build the mesh in Blender.
Assign the materials in Blender.
Build the groups in Blender.
=> Tip : The dress has to have the same groups and internal group names as Roxie for all groups covered by clothing.

=> Tip : rThigh and lThigh groups may NOT touch.
Deepen the hip group between them to keep them separated. => THIS is IMPORTANT.

Goto Poser and use the fitting room.
Do NOT do the FIT.

Load the Prop, load Roxie and click create figure.
Select the bones required.
Tip : For a dress like this?
Hip to neck
Exclude head and eyes

Arms up to and including hands (not the fingers)
And lower up to and including both thigh

Shins feet and toes can be excluded.

Select the Morphs you want tin the dress.
DO NOT use the AUTOGROUP function.
Check : ZERO figure.
Click OK

Go back to the Pose room.
Delete the original object file.

Select the newly created Dress and click conform to and select Roxie.

Save the dress to library.

That's it in a nutshell.

Edited : If all goes well, only the hip-thigh W-Maps need some repainting in Bend, twist and side-side

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!