Just a guess from reading the wiki, but this should be a stab in the right direction:

MakeNamedMaterial "ball_1/Preview" "string type" ["light"]
"float gain" [100]

"color Kd" [0.576470414797 0.576470414797 0.576470414797]

"color Ks" [0.0250000003725 0.0250000003725 0.0250000003725]

"float uroughness" [0.258086156304]

"float vroughness" [0.258086156304]

Not sure if the Ks, Kd and roughness parameters carry over. The colors might have to be Kt, Kr.

Software: OS X 10.8 - Poser Pro 2012 SR2 - Luxrender 1.0RC3 - Pose2Lux
Hardware: iMac - 3.06 GHz Core2Duo - 12 GB RAM - ATI Radeon HD 4670 - 256 MB