I can tell you step by step how to do this, and in case you are confused with what I mentioned above, I will write them step by step:

Select your two Rogers with the highest star rating that you have and send them in the Cloning Room.

You need only two Rogers in the Cloning room to start the process, so there is no need to move more and stop your money making process or food making process or so.

Slowly the Rogers will start producing clones, but this will take time and if you only have three star Rogers it will be a fairly low chance that you get a four star Roger from it.

Once you can build more Cloning Rooms try to clone more Rogers and eventually you will get better ones.