Hi @Walt_Lederie,
Have you made sure to enable your Samba share on the X45 prior to trying to add it as a storage device? I would suggest looking over the Cocktail Audio X45 Manual, specifically on page 49 for instructions on how to enable and access the Samba share.
After enabling the share, then on the Roon side you would need to add the share location, typically this is smb://HOSTNAME/SHARENAME or \\HOSTNAME\SHARENAME. Please take a look at the examples from the bottom of the page. I would try connecting as a “guest” if connecting without a username/password is not working.