Re: When were the ROKU models 2, XD/S and 2XD released|?
The Roku 2 HD/XS/XD were all released July 2011. The Roku LT was Nov 2011, and an updated LT and the 2500 (Roku HD) was April 2012.
For Roku 2 (with no initials after the number) the first version (2720) was Sept 2013, and the last version (4210) was April 2015.
Of the ones I've listed above, only the 2720, 2700 (Roku LT) and 4210 are still considered supported by Roku. They still get the latest OS updates. The rest are considered legacy, and no longer supported. And of the ones listed, the 4210 is really the only one that stands a chance of being usable by the newest channels. However, even it has a limitation, in that it doesn't support 1080p/60. At 1080 resolution it is limited to a 30 Hz refresh rate. At 60 Hz, 720p is its highest supported resolution.
Dan Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.