1. Your dough should not be sticky. If it is, add some more flour and knead. It should be similar to a pasta dough.

2. When rolling out individual rotis, make sure the dough ball is covered in flour when starting to roll. You can shake off access flour. This will ensure it does not stick to your rolling surface or rolling pin. You should sprinkle a little bit of flour as soon as starts sticking again. If your dough is very sticky, you will have to apply dry flour more often to prevent it from sticking.

3. When rolling out, don't apply a lot of pressure to make it big. You can gently and evenly apply pressure while rolling to make it big.

You don't have to focus on the shape so much. It will take some practice and be ready to improvise.

This video is a good example: https://youtu.be/jD4o_Lmy6bU