I think I have the same problem.
Just received my new Express 4K+ today. Says for best service, connect HDMI to a port that supports HDCP 2.2. TV (VIZIO 507-G1) lists 4 ports:
as you can see ... 4 ports designated 2.0 (ARC, CEC),
HDCP 2,2 is mentioned but I don't know which of the 4 ports is/are HDCP 2.2 capable per Roku requirement. Is the spec suggesting Any/all qualify??
Each HDMI port is numbered on back of TV. 1 [ARC], 2, 3 and 4. Hoping one of them is the best for the ROKU. Thanks in advance for any help.