Hi Bradspal,
You are the first to report this problem on Sony Bravia.
On the thread:
The Roku Channel is temporarily unavailable on Samsung TV
there are about 12 of us with the same problem- the Roku channel no longer works on Samsung Smart TV but it used to work. Also, the Roku channel works well on smartphones, desktop computers, etc. Other apps still work on our Samsung Smart TVs. Our Samsung Smart TV problem has been escalated to Roku second-level support who are working on the problem but no solution so far.
FYI.