First, suggest you edit your post to remove email address. This is a public forum and spammers cruise places like this collecting publicly posted email addresses. Click the 3 vertical dots at upper right corner of your post to find edit option.
You don't say if this is a Roku device connected to a non-Roku tv, or a Roku TV with Roku built in.
Look for a tv control called Picture size, Zoom, or something similar to see if this is something you can adjust on the tv.
Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T