If you are removing the roof rails and installing the deletes, you need to remove the rails first, then the inserts.
If you are removing the inserts and installing the roof rails, now comes the tricky part. The inserts are held in the roof channels with clips that slide over pins in the channel. Whatever you do, do not try to pry the inserts up.
1. Start at the rear of the channel. 2. Using a non-marring tool (plastic fork, wood stick, plastic putty knife), careful lift the -inside- flap of the insert. 3. Using another tool or tools, gently tap or push the clip off the pin. 4. After a few clips are loose, you can lift the insert and get easier access to the clips. 5. The very front of the insert has a pin that fits in a hole by the windshield. Gently pull straight up to remove.
As you can see the pins are very small. Don't use excessive force.