DomainRole 0 is “Standalone Workstation” and DomainRole 2 is “Standalone Server”. What the action is checking is that the machine should not be joined to a Domain before capturing it.
From what I recall, Microsoft’s recommendations are not to avoid sysprepping a domain-joined machine. Basically there are some problems that can come up, especially if Group Policy is applying settings that might cause Sysprep to fail. I recommend you should unjoin from the domain before trying to Capture the machine.
Re-joining the Domain when you deploy the image to computers is something you’d configured on the Image Profile after you capture and upload it to your BigFix server.