Flattening dough for Roti into a perfect circle takes a bit of practice. When i started out cooking, i would make a shape and then use an inverted bowl to cut away the edges and get the perfect shape. This process involves taking a bowl with sharp-ish edges and Set in on top of the flattened dough and the edges will get cut out.
However nothing beats the joy of flattening the perfect circle pancake. The video below should help you with that.
If you want to improvise the trick is to press it from all directions.
Use a flat surface. The kitchen slab surface will do just fine. Just make sure its clean and put some dry flour to make sure the surface does not become sticky.
Use a cylindrical bottle in place of the wooden baton ( Belan). Be careful the bottle could slip out of your hands. Take adequate precaution.
You can also use a bowl with large flat base to press on the dough and create the flat shape. The results may not be optimal like the other methods. However, you can fine tune by using the bottle technique mentioned above.
In both cases make sure you apply dry flour to make sure the wet dough does not stick to surfaces.
In case you don’t have the tools that are shown in the video you can pick them up HERE.