Hi!
There are actually two rooms in this template. First, there's the rDesktop. That's the game! But there are also a room called rInit, that initializes everything and then send the player to rDesktop. If you want to change the room size, you need to change it in both rInit and rDesktop. Also, since this template uses viewports, you need to adjust that as well. Go to the settings in rDesktop and change the width and height of Viewport 0 to 1280 and 720. Remember to use 1280 and not 1300, since template uses pixel fonts. They don't scale well to odd numbers.
This should resolve the issue!