If your channel absolutely must have the same look and feel as your existing smartphone apps, then using roScreen is what you need to do. roImageCanvas is not really fast enough to be used seriously for a UI, although there have been a few channels based on it, it is essentially clunky and sluggish.
It isn't that difficult to build your own components in roScreen. Not knowing what your existing smartphone apps look like, of course there is a limit to the kind of advice we can give you. The best advice I can give you is just to start working on it, and ask questions if you run into trouble. roScreen is good for creating slick user interfaces with the kind of smooth motion you might find in an iPhone or Android app, especially if you use the double-buffering mode.
Joel