Roti sabzi can be a good meal, but it depends on what the roti and sabzi actually are.
Two whole wheat rotis with mixed vegetables, dal and salad can be fibre rich. Three refined flour rotis with potato and pickle are a different story. The words roti sabzi alone do not tell you the fibre content.
Start with the atta. Whole wheat is better than maida. You can sometimes mix in besan, jowar, bajra, ragi or soy flour if it suits taste and digestion. Then look at the sabzi. Increase non-starchy vegetables like bhindi, beans, cabbage, methi, spinach, lauki, tori, carrot and capsicum. Potato can stay, but it should not be the only vegetable every day.
Add dal, curd, sprouts or chana when the meal needs more substance. A small salad can improve crunch and fibre, but cooked vegetables may suit sensitive stomachs better at night.
Do not make rotis huge and vegetables tiny. The proportion matters.
A better roti sabzi meal is familiar, affordable and realistic. Fibre improves when the plate has variety, not when one food is blamed or worshipped.
For medical conditions, use this as food education and keep personal targets with your clinician.