Roles: Owner & changing roles of other invitees

I added a field that is identified as only admin can write.  The problem is I need the owner to be identified as an admin because she is the one that needs to complete that field as part of an approval process.  Currently under permissions, owner does not show up.  How can I change field to either include owner (which I thought they had all access) or change owners role to include admin?  Thank you!