Denise Petski Senior Managing EditorRoswell, New Mexico co-showrunner Carina Adly MacKenzie is exiting as co-showrunner of the CW’s Roswell, New Mexico ahead of the third season “due to fundamental differences”, MacKenzie said Friday in a statement posted on social media.In her statement which reads in part, MacKenzie said, “I have made the difficult decision to resign from my role on Roswell, New Mexico.