There are two ways to indicate that no room is needed for a course via Time Schedule Construction. Both involve asterisks.
Option #1: Select "non-general assignment classroom" and put an asterisk in the "building" field and the "room" field.
Option #2: Select the " * " under meeting days. Courses without meeting days/times cannot be assigned a room.
Changes made via Time Schedule Construction are more durable than changes made by the Academic Scheduler (i.e., these changes will carry forward to the next qtr/yr).