I don't think so, if there was such a thing it would be part of the deployment api https://docs.developers.optimizely.com/digital-experience-platform/reference/ but there's no features for doing any restart same as in the passportal.
I think the only way to get a rolling restart to happen is book them in with Optimizely support to go through all the scaled intances and restart them one at a time.
As Scott mentioned, it looks like the only option right now is to arrange the rolling restart with the Optimizely support team however enabling self-service rolling restarts has been added as a feature suggestion via the Optimizely feedback portal here:
https://feedback.optimizely.com/ideas/DXCS-I-303
It's tagged as "Future consideration" so it's unlikely the feature would be rolled out in time to help with your current situation but it would still be worth giving it an upvote to help the Optimizely product team to prioritise that feature.
We need to temporarily schedule a rolling restart once a night while we work on a permanent fix for an issue. We can normally do a full restart from the PaaS portal, but that takes the site down, while a rolling restart does not. Is there any way to initiate a rolling restart like this?