One way is to ask the developer via the contact information provided in the application's Google Play page.
Where an application or game has a free- or paid-version, you could just try the free version. Unless it's stated in the description that the paid version actually supports higher resolutions, it's usually a safe assumption that if the free version looks a certain way, the paid version will look similar.
A final way is to simply buy the application and try it within the 15 minute refund period. If you're not pleased with the way the application or game is formatted for your screen, simply refund it. Keep in mind, though, that you're only allowed to refund an app once. If you re-install it after refunding, you will no longer have the option to refund and will be billed immediately.