How to change root component rotation?

In the learn project shootergame, open the blueprint Game/Blueprints/Weapons/WeaponGun, i found that can’t modify Mesh1P’s rotation. But the Mesh1P is still upward like Mesh3P, Mesh3P’s roll is -90.

If i create a new blueprint of class ShooterWeapon_Instant, i can’t set Mesh1P’s roll, can’t let Mesh1P upward.
How to set Mesh1P’s roll?