I believe I saw your images on another website asking this question. (someone forwarded me some images with a link to question). Either that, or someone else is having the same bad day.
If your TV is under warranty, then you will need to contact the manufacturer and see if there is something they can do. (https://community.roku.com/t5/Manufacturer-Support-Warranty-Resources/Contacting-Support-for-Your-Ro...).
If your TV is out of warranty, or you are adventurous, then pull the power plug first. Straighten out the 4 spades (only 1 looks bent.) Then slide that plastic piece back in over the metal spades. (this is really just an insulator and guide).
It really is only going to go in one way. If you need a reference, just get a usb stick and see how that plastic piece fits into the stick. Whether or not the port will again be usuable, who knows. But if you can get that insulator guide back in, will hopefully make that message go away. These things are very fragile so go slow and don't aim for perfection, just straight enough for the piece to slip back in while lined up with those spades.
Otherwise, you can certainly buy USB ports online, disassemble the TV and do some soldering. (only you can determine if you can do this.) Otherwise, with the price of TV repairmen, may end up being cheaper getting a new TV.
You can also try going into RokuTV settings and disabling the Auto-launch setting. (Settings/System/USB Media/Auto-launch (Off)
I think the only real way to disable the USB port completely would be to remove it from the board (de-solder the connection).
Wish I had better news for you.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941