How do I copy to the root of a network share with Robocopy?

I'm trying to copy very large amount of small files from one folder on my local drive array to a network share, and after trying many different methods of copying files I decided Robocopy might be best, but I keep getting weird errors that indicates Robocopy is trying to modify the target folder in same way, which it can't do because the "folder" is the share on the target server.

I'm running this command:

robocopy C:\Users\brian\Documents\domains \\dev\Domains /TEE /MT:64 /e /is /r:1 /w:3 /fft

Which works if I try to copy to a sub-folder on \\dev\Domains, but not to just \\dev\Domains, which is where I want my files to be.

To be more literal (in case I am wrong about my assumptions of what Robocopy is doing internally), this is the exact error message:

ERROR 5 (0x00000005) Changing File Attributes \dev\Domains\ Access is denied.

I tried this with things like C:\Users\brian\Documents\domains\* (thinking maybe some rsync tricks will work here) but that just causes syntax errors for Robocopy.