Rolling Game Project transition to Side Scroller?

https://drive.google.com/drive/folders/0B9b7Gw4N64LCUlRVbG1LLTdxZkE You can download this project it’s made by Elhoussine Mehnik 3D Projects - Elhoussine Mehnik
There are many ways to do that. You can put physics constraint so that it moves only in two axes. Or should add movement input only to two axes let’s say x and z.

So, if anyone could tell me just a basic way of how this could be done.
Or if I should just create a side scrolling project create the level, then Import to my Rolling game?