Think of your user - do you want them to type manuscripts, pages of text into the app using the roku remote? If there are common phrases, add a button for those to the keyboard to autofill/autocomplete, like for 'comcast.net' if it's an email address.
Maybe you're trying to avoid doing this, but perhaps some sort of custom dialog that pulls those parameters out of the URL separately ( as far as the user sees) and can be adjusted. I'm guessing there are a finite number of parameters out there. A lot more work for you but as I user, i'd much prefer it to that keyboard even if I could scroll over.