Roan is Lucas' true name from the time before he lost his memories.
Roan is Glinda's husband and a key element of her plan to take down the Wizard. He's been transporting young witches on Glinda's behalf. During one of these runs, he had been stopped by the Wizard's Guard and forced to kill some of the men, protecting the girls' escape.
In order to keep the plan a secret, Roan took a pill to suppress his memories, given to him by Glinda.
Once reunited with Glinda in Calcedon, Roan regained his memories through a kiss. However, since regaining the memories, he feels conflicted and torn between Dorothy and Glinda. After Dorothy tried to kill Glinda, the Witch of the North gives Roan a knife and orders him to kill the girl and free himself from her spell.