I’m having this same problem as well. It doesn’t happen with my Roku Ultra and a 4K TV but does happen with a Roku Express and a 1080p TV. Resetting the Roku makes it go away, but only until I switch to a channel with a different resolution and back again.
Still no word from Tablo on a fix?
I’m having the same issues. Just got my 4th gen Tablo. I also have an older Roku streaming device. It seems like the issue may be with the Roku not adjusting the resolution correctly. If the signal is 480 or 720 then the picture does not automatically adjust to my tv screen. Only if it’s 1080 resolution, then picture is fine. It looks like I may have to upgrade my Roku?
4th Gen Tablo, tried on 2 diff Roku sticks that are about 5 years old. Tried on older Samsung and 5 year old Insignia TVs, HD channels look good, 480 channels appear in same very small unwatchable box in upper left corner that others have reported.
I have a new Roku Ultra on the way and will report results on various TVs using that Roku box when it’s up and running.
I’m ready to cut the cord but I’d prefer a workable, free live TV to be in place before I kiss cable goodbye.
Update: Forgot that one of our TVs is a 720p TCL Roku TV. So… tried Tablo there and as expected, the sub channels (less than 1080p) all appear fine. They are NOT playing in tiny box in upper left corner like we’re seeing on our other higher res TVs with Roku sticks.
Still waiting on arrival of Roku Ultra and will report results with that when I can.
I’m really rooting for Tablo, it’s a neat and affordable device! I just need to see a few of these bugs ironed out soon to feel comfortable moving forward with their tech. Otherwise, it’s going back.
After testing internally, our team has confirmed the shrunken video/green screen behavior is a known issue specific to certain Roku models (usually ones that are older or have lower memory).
This issue is also present in other video streaming applications besides Tablo.
We’ve reached out to Roku to make them aware of this issue which hopefully can be resolved in a future Roku OS update.
In the meantime, power cycling the Roku does resolve the issue temporarily but upgrading to a more recent/powerful Roku should resolve the issue entirely.
UPDATE: Received my Roku Ultra yesterday, connected to Yamaha TSR-7850 AV receiver which connects to Samsung 7 Series 4K TV. All channels including 720p & 480p sub-channels appear full screen.
Will attempt to connect Roku Ultra to our other TVs that showed the low-res channels in small box in upper left corner of screen and report results here.
I read Tablo’s response in this thread, re. it’s Roku’s problem to solve, and although I’m totally unsatisfied with that response, I fully intend to follow up with Roku. I have 4 or 5 approximately 5 year old Roku “sticks” that are having this issue and I’m not excited about the prospect of having to upgrade all of them.
UPDATE: Following up on a suggestion that this issue may be related to available memory on the Roku devices, I removed most of the apps and restarted my Roku. No joy, the problem persists.
Will keep pushing for a solution from Tablo & Roku.
Do a search for something like “Roku playing videos in top left of screen”. Changing up the search words can give you different results. Your not the only one having issues. I’m using a 2 year old or so Roku Ultra and have not had this problem.
UPDATE: I had a 45+ minute chat session with a Roku customer service representative.
It went like this: Change display from auto to 1080, Run software update, Restart Roku, Rep says try it now.
Tablo low-res channels look good showing full screen (very nice). Try movie on HBO Max app HD movie showing nicely. Go back to Tablo low-res channels now reverts to appearing in an unwatchable small box in upper left corner of screen with remainder of screen bright green background.
At this point my cell phone craps out and the chat with Roku rep is of course over.
So… looks like Roku’s fix is change display settings EVERYTIME you want to watch low-res Tablo channel.
That is not a fix!
Search results seem to indicate that Roku Ultra does not exhibit the problem and as per my previous posts my new Ultra does not have any problem displaying 480 or 720 content via Tablo app.
Definitely not a fix. Got rid of my old Roku and got a new Firestick. No issues whatsoever with display size.
UPDATE: The Roku Ultra seems to show 480 & 720 Tablo content nicely no matter which TV I connect it to.
So… here’s what I’ve learned:
(1) Tablo app has problems showing 480 & 720 content on some Roku devices.
(2) The problem does not seem to be related to how much memory is free on the Roku device.
(3) The problem does not occur on brand new Roku Ultra.
(4) Tablo says it’s Roku’s problem.
(5) Roku customer service is offering same old “reset display resolution”, reboot, rinse and repeat, “not a fix” fix . AND you’ll spend a painful 45 minutes in online chat with Roku only to realize you know more about the situation than the Roku csr does 
(6) Everyone say’s newer Roku devices don’t experience the issue BUT no one is providing any definitive details on which devices do or don’t have this issue with Tablo
So… now I’ve ordered a new Roku Streaming Stick 4K. We’ll see how well that works!!!
NOTE: my $99 Tablo cord-cutting adventure is now plus about $150 in new Roku devices.
UPDATE: New Roku Streaming Stick 4K works well on all TVs in the household.
All Tablo channels regardless of resolution (1080 vs 720 vs 480) ARE properly displayed and totally viewable.
So… Tablo really needs to responsibly label the Tablo 4th Gen as NOT COMPATIBLE with Roku stick devices more than x years old.
Or maybe, how about a list of compatible Roku devices (by model number).
I’m pretty sure that I would not have purchased the Tablo if I had any clue about the Roku compatibility issues I’d be facing and the hours I’d spend trying to diagnose the Tablo/Roku screen resolution problems.
I still have until Jan 31 to return the Tablo & 2 additional Roku’s I had to purchase just to evaluate the Tablo.
I don’t think tablo is responsible for any Roku OS release or update that could render your roku obsolete. Of course I always spend extra on the ultra and my 2013 roku 3 ultra still works with the gen 4 app using WiFi. As does my 2015 4210.
General “word to the wise”. If you want the longest usage out of a Roku, then buy the top end model. I’ve still got Roku 3s (which are incredibly old) that work fine.
Other advice, Roku TV, bad idea. Always a bad idea. Smart TVs in general, a bad idea, but we’re stuck with that “because”.
It was hard to beat the old roku 3 hockey puck from 2013. The 4210 roku 2 from 2015 was nothing more then a roku 3 with a IR remote instead of a WiFi direct remote.
The newer model ultra’s 4660 and newer have better video quality.
As as a test I’m watching Live TV(720p) on my gen 4 using a roku 3 and WiFi 2.4 Ghtz. Still no burps after 30 minutes.
How can this be a Roku problem? My original Dual Lite fills the screen properly on sub-1080 broadcasts. The Gen 4 does not. Both are using the same Roku Stick. If the old Dual Lite can do it correctly why can’t the new Gen 4 do it?
OG style devices worked very very very very differently. They avoided “the mess” that the new device is trying to take head on. You’ll have to decide who is winning with regards to the latter. Design choices.
Legacy gateway devices used h.264 compression. Users wanted the picture quality of native MPEG2 broadcasts. maybe you devices just accidently turned into road kill. Only tablo and Roku know for sure.
I’d be careful saying “users wanted the picture quality of native MPEG2”, because, at least for anyone with technical experience, you know the sacrifice in compatibility and flexibility that comes from that. That is, “do you want quality of picture that works ‘sometimes’?”, or “something that works for many cases, allowing for more features as well?”