Can I sell RPGs I make with the OHRRPGCE?
Yes. You can distribute your RPG files any way you choose, and that includes selling them. The OHRRPGCE engine is GPL licensed, but your own game and scripts are data files, and are not linked to the OHRRPGCE code, so the GPL does not have to apply to your game.
If you plan on selling your game, you should choose COPYRIGHT as the license in the Distribute Game menu. That will automatically add a simple copyright notice to your readme file.