Thanks to ScienceGirlLP for sending this information

Roswell will continue with another new episode in 2 weeks (Feb 26th). Next week UPN will air a special 2 hour Buffy the Vampire Slayer in the Roswell time slot.

Here is the episode description for Chant Down to Babylon from the TVguide.com website.
Michael, Jesse and Valenti call on a discredited doctor to help the wounded Isabel. Also, Clayton Wheeler (Jack Donner) undergoes an amazing transformation and soon finds himself drawn to Liz; and Jesse quizzes Michael about Isabel’s alien roots. Meris Wheeler: Morgan Fairchild. Michael: Brendan Fehr. Jesse: Adam Rodriguez. Isabel: Katherine Heigl. Liz: Shiri Appleby. Valenti: William Sadler.