As a side comment, even if you get it to work, it is not the best setup, imho. All music is output from the Roon Core, so if the music was on the Innous it would be first sent over the network to the nucleus, processed and then sent back to the Innous for playback. The closer to the Core the music is located the smoother and quicker operations will be, in my experience.
I would suggest trying the smb://IP_ADDRESS notation as @Rugby noted to see if it will help. If you have a username and password set up for that share, have you made sure to enter it into Roon as well?