GMPRN
Now that you have reset the APN and have IPv4/IPv6 showing, are you able to get any other devices (laptop, husband's phone, etc) to connect to your hotspot. [Now have to verify your hotspot is actually working].
If you can verify that your hotspot is working, try performing a Network Connection Reset from within Roku. (Settings/System/Advanced System Settings/Network Connection Reset, Reset Connection).
Also, restart your phone and perform a Connection Reset there as well. (Settings/More/Network Settings Reset)
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If still can't connect, try using the 2.4ghz band of the hotspot. (Settings/Mobile Hotspot and Tethering/Mobile Hotspot Settings/Setup Mobile Hotspot/[select 2.4ghz band for AP band] )
If still having issues, try configuring the hotspot to use IPv4-only rather than IPv4/IPv6. ( Some of the TMobile hotspots have issues resolving the IP protocols when both are enabled, and others are fine. Kind of device specific.)