Over-kneading roti dough results in a tough and elastic roti, making it difficult to roll out and resulting in a chewy texture after cooking.
Kneading develops the gluten in the flour. Gluten is a protein that provides structure and elasticity to dough. When you knead roti dough, you're aligning the gluten strands, making the dough smooth and pliable. However, over-kneading causes the gluten strands to become too tight and overly developed. This makes the dough excessively elastic, causing it to resist rolling and shrink back when you try to flatten it. The resulting roti will be tough and chewy instead of soft and tender. The ideal roti dough should be smooth and elastic, but not overly so. It should feel soft and supple to the touch.
To avoid over-kneading, knead the dough until it comes together into a smooth ball, then let it rest for at least 30 minutes. This allows the gluten to relax, making the dough easier to roll out even if you kneaded it a bit too much initially.