This tutorial will show you step by step how to replace the default theme logo with your own on Plone 5.0 website
Text'n'Roll responsive theme comes with default Plone logo.
You can replace it with custom image as you would do it in default Plone: go to account menu in the side toolbar, then choose Site Setup -> Site -> Site logo. Upload your image there.
Now when you return to the Plone interface, you'll see the new logotype.