Actually I've figured it out using JS. Although the method below is simple, it does lead to complications such as inserting paragraph tags into list items and a lot of line breaks etc... I guess you can strip that out later in php. Here's the code for anybody that needs it:
$("#richTextField").contents().keydown(function(e) {
if (e.keyCode === 13) {
richTextField.document.execCommand('formatblock',false,"P");
}
});
Or you can just do it like this, which works better in my opinion because with the code above if write something in but don't hit enter, you get no paragraph tags at all.
$("#richTextField").contents().keydown(function(e) {
richTextField.document.execCommand('formatblock',false,"P");
});
Only way to do it that I could find. If anybody know of another without going into javascript and monitoring for the 'enter' key please post.