Roku 3 (4200) is an HD unit which does not support 4K. The Roku 3 supports HDCP 2.1 (or maybe 2.0, I no longer have one to check), it does not support HDCP 2.2 as it does not need to.
HDCP 2.2 is only needed to send 4K content to the tv, something the Roku 3 cannot do. The Roku 3 can still send HD content to a 4K tv, because the tv's HDCP 2.2 is backward compatible with earlier HDCP versions so it can accept non-4K input.
Roku Community Streaming Expert I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well. If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X