I logged out and back in and it worked. The account I'd logged in on immediately before actually has no rokus linked. Theory: Some cookie must have got stuck somewhere, because I was definitely logged into my account with 6 linked rokus when I saw the message. I'll leave this here for the Roku web maintenance gods to suss out.
Yes let me assure anyone at Roku who might be interested, there is definitely a bug when logging out from one account and into another and then accessing the developer zone. I logged out from Account A ( my "user" account) and into Account B ( my "developer" account) and I tried to access a specific channel and saw a weird error message, then I noticed in the upper right the dropdown said "Welcome <Account A's Name>" even though I am logged into Account B.