The rumored Roku 4 streaming player may support 4k video streaming as a means of competing with the Amazon Fire TV, which is confirmed to have 4k video support. A report from ZatzNotFunny cites documents sent to the FCC saying that Roku will come up with a device that will feature Ultra HD video support. 

However, the documentation reveals that the device might not be the actual Roku 4 and may instead be upgraded versions of the Roku 2 and Roku 3. It is important to note that these are still documentation files and not the actual product under development so it is possible that the "upgraded Roku 3" might be called the Roku 4. 

The FCC documents list six different models. The first two (4210X and 4230X) refer to the Roku 2 and 3 but there are four others that have no corresponding Roku models: 4200X1, 4210X1, 4230X1, and 4205X1. It is possible that these refer to upgraded Roku 2 and 3 devices and the official Roku 4, all with 4k UHD support.  

Another report from UKRokuChannels stated that 4k support was listed on the official Roku website but this has since been taken down. The report was able to snatch a screenshot of the post, which further implies that Roku does have plans of 4k video support somewhere down the line, although it is uncertain if the Roku 4 will be the device to implement it. 

CinemaNow has also posted details for the Roku 4, although it is possible that this may simply be a typo as stated in a report from FierceOnlineVideo. However, the site states that the Roku 4 will offer four free HD rentals from Oct. 1, 2015 to April 30, 2016, hinting that the advertisement could be referring to the actual Roku 4. 

If the latter is true, then the Roku 4 might be released soon, with Oct. 1 of this year being the earliest that the company may launch the device.