In Royal Tickets, you can insert canned responses and even edit the content before sending your reply.
To insert a canned response, open a ticket and tap the "Reply" button.
Now tap inside the text editor where you want the canned response to be inserted.
The context menu will pop up and include an option "Insert canned response". If this option is not immediately visible you might have to tap the arrow button on the right side of the context menu to get to it.
A new screen will pop up which let's you choose one of your articles to be inserted. If you cannot find the one you're looking for, scroll to the bottom to load more articles.
Now simply tap the article you want to insert in your reply and you're good to go.