I've just made it as normal: eggs, cream and milk with a tablespoon of sugar, which I think is around 40g, as it would feed 4, it's not too bad, but I'd guess just substituting a sweetener would work perfectly well, I don't think that much sugar would affect the consistency in any way.
If you just substitute the sugar for a good quality sweetener, like erythritol, that would work fine for your standard recipe.
I might be tempted to reduce the milk a little and increase the cream, too.
Thanks both. I'll have a go at this later.
I invented my own roulade yesterday. I'd made oopsie bread and added sweetener to half of the mix, spread it on a baking tray in a vague rectangle and cooked it. Simmered some frozen raspberries with sweetener and let them cool. Spread the oopsie with the raspberry puree, lots of whipped cream and some fresh raspberries.. yumm. Hubby didn't even realise he was eating low carb