Yes the Tablo dual lite is compatible with commercial skip when using an attached hard drive. If you are using the cloud storage, you will need to verify that it is compatible with Tablo Support or by another user here who is using the cloud storage.
Are you seeing a yellow dot and text stating that “Commercial skip is ready” when selecting a recording to watch? If there isn’t a yellow dot, then there should be a red or gray dot. Red dots should give a reason why commercial skip failed and gray dots are for programs that aren’t eligible for commercial skip processing. Tablo doesn’t always get it right, but if commercial skip processing has taken place you should see one type of indication on each program.
If you aren’t seeing any indication of commercial skip processing, then you might try deleting the Tablo app from your Roku, reboot the Roku and then reinstall the Tablo app. Check the settings screen and confirm that commercial skip is turned on and try recording a new show. Once the recording has completed, it may take an hour or two before commercial skip is available.