Remove root certificates from iPhone

If nit via profile, I am aware of no supported means to remove a built-in certificate in the Apple-provided trust store.

• Disable the certificate at Settings > General > About > Certificate Trust Settings. If you do not have the section showing Enable Full Trust For Root Certificates, there are no additional certificates.

Trust manually installed certificate profiles in iOS, iPadOS, and visionOS - Apple Support

• To remove a Profile that installed the certificate, go to Settings > General > Device Management, and remove any installed profiles there. If the profile is being managed, you may not be able to remove it and would need to contact the originator that installed the MDM software.