From their site:
“Our Pluto TV channel supports Firmware 7 or above. You can check this on your Roku by going to your “Home” screen, click on “Settings”. Then, select “System”. Click on “About” or hit “right arrow” to view your current software version.
Our channel is now available on these Rokus (running firmware v7.0 or above):
Our channel is not yet available on:
All Rokus with firmware versions below v7.0
All Roku TVs – (including TCL Roku-enabled TV’s)
Roku 1 and Roku 2 with model numbers 27XX
2011-2013 Rokus with model numbers of 2400, 2450, 2500, 26XX, 30XX, 31XX
MHL Streaming Stick – model number of 34XX”
Have you tried Pluto TV? Comment below.