Vegan egg substitute in sweet roll dough
You can use either chia seeds or ground linseed.
Mix a tablespoon of chia/linseed with 3 tablespoons of water and let it sit on the counter for about twenty minutes.

That mixture will replace the egg in almost any recipe for bread/mixed cake.

The rest period is important, as it allows the water to soak up the sticky proteins from the linseed/chia.