No there is not any built in videoconferencing or add on software/hardware from Roku.
Best option is to get a small cheap computer/tablet (maybe 2nd hand) and attach to TV using HDMI cable. Need to buy peripherals like external webcam, maybe mike and speaker puck, and wireless mini keyboard trackpad, and then install Facebook, teams, google chat meet duo, zoom etc. Should be possible to mount computer on back of TV with brackets, zip ties etc.
Not a Roku employee