Users of current-generation devices will now be able to find YouTube in the Roku Channel Store. Current-generation Roku sticks include: Roku LT, Roku 1, Roku 2, Roku 2 HD, Roku 2 XD, Roku 2XS, Roku 3, the Roku Streaming Stick (both HDMI and Roku Ready versions) and the Roku HD model #2500.
From Roku's website:
Remember, you can also send YouTube videos from your Android devices, iPhone and iPad to your TV, when you’re connected on the same WiFi. Perfect for those situations when you’ve been sent a link of the latest YouTube sensation or when you don’t want to huddle with others around your phone or tablet.
Image: from Roku website