CSV import does not currently support virtual attributes.
The below fields are virtual attributes on the Roadmap ITEMS (RMI) object except 'sync' attribute from your list. However, though 'sync' is a physical column, it can't be updated to 'true' until it is linked to some investment.
The actual field that produces value for the above 3 fields is 'linkedInternalId'. You can observe the same thing in the patch payload when you try to change the linkedTo for any of the RoadmapItem. So what you were trying here basically is the ability to update 'linkedInternalId' via CSV import. By definition, this linkedInternalId is a private attribute and CSV import never supports updating a private attribute. If a user tries to do so, it becomes a bad request and throws below error in CSV import (not just RMI, any private attribute of any object would give the same error if we try to import).
"IMP-1005: Column 'linkedInternalId' not supported for import."
As per the current clarity code we can't make this 'linkedInternalId' public either nor CSV import be relaxed for private attributes. This would an enhancement which is only possible via a code change for a future release.