Roti dough made the night before behaves differently from dough made an hour ago. Several processes continue in the bowl while it sits, and they do not all work in the cook's favor.
Hydration continues long after mixing
Water takes time to penetrate flour particles fully, and a dough that felt correctly hydrated when mixed will feel wetter after resting as absorption completes.
Whole wheat flour absorbs more slowly than refined flour because the bran fragments take up water gradually, so atta doughs change more over a rest than white flour doughs do.
The practical result is that overnight dough often needs a dusting of flour to handle, even though nothing was added to it.
Gluten relaxes and rolling gets easier
Kneading aligns and tensions the gluten network, which is why fresh dough springs back when rolled. Resting allows those bonds to rearrange and release that tension.
A rested dough rolls thin without fighting back and holds its shape, which is the main reason recipes specify a rest even when it is only twenty minutes.
An overnight rest takes that relaxation further, which is why refrigerated dough can feel slack and unstructured. Kneading it briefly before rolling restores enough tension for the bread to hold together.
Enzymes keep working in the cold
Flour carries enzymes that break starch into simpler sugars, and they slow in the refrigerator without stopping. Overnight dough contains more free sugar than it did when mixed.
That extra sugar browns faster on the griddle, so refrigerated dough produces darker spots at the same heat and can look overcooked while still being underdone inside.
Oxidation changes the color
Dough exposed to air darkens over hours as compounds in the bran oxidize, giving a greyish cast that is cosmetic rather than a sign of spoilage.
Covering the dough tightly or pressing plastic against its surface limits both the darkening and the dry skin that otherwise forms and then shows up as hard flecks in the rolled bread.
Working with cold dough
Cold dough is stiff and tears rather than stretching, so letting it come back toward room temperature before rolling avoids most of the handling problems.
Because the dough contains no preservative and is handled by hand, general refrigerated storage guidance applies, and a batch that smells sour or shows any surface growth should be discarded rather than cooked.