Chocolate Swiss roll is a bit tricky. Why? Because cocoa powder complicates things.
Cocoa powder makes sheet cake less stretchable, so you have to be careful not to overbake the cake. Even slight overbaking makes the cake crack when you roll it.
My Swiss roll is very stretchy. It can stretch and bend into a roll without cracking.
The flexibility is due to the way the eggs are beaten. Egg whites are whisked to firm peak stage, then yolks are added 1 at a time and whisked thoroughly. Compared to the whole egg or chiffon method, this makes a cake that's more stretchable.