To delete a room layout you will need the permission Classroom Management: Administer All Room Layouts or Classroom Management: Administer My Room Layouts. If you don't have this permission, ask your admin team to assign it to you.
Navigate to the Lesson Dashboard for the lesson that is scheduled in that room. Click on My Classroom.
Click on the three vertical dots in the top right corner.
Click Edit Room Layout.
Check that you have the room layout you want to delete on the right-hand panel and click on the red Delete Layout button.