Is there a way to find when company/startup is sold? Like does Delaware registers when companies are sold? I'm looking for a roboticist who's company just sold successfully and she's ready for a new big thing. Any help is appreciated. Thanks in advance
No. Unless the person was an officer or director, you would likely not find their name on any official document (and not in DE unless it was a DE company).
Search for the person on LI - or people connected to that person, and search for the recent news on the company.
If the person is a significant beneficiary of a recent exit, you may be wrong that she is "ready for a new gig". If critical to that company success, that person may be subject to non-competes, employment agreements with the acquirer, or just ready for a break.
There's little obligation to make any information available about a private company that has been sold, including by whom, to whom, etc. Using tools like LinkedIn Recruiter, you can see profiles who have self-identified as looking, which is not generally public information. You can also see when someone changes jobs, though that may be too late. You may only be able to signal that you're interested and post that information where you know robotics people look for jobs.
If you're targeting an individual whose identity you know, it's different. But @Dane is quite correct, just because someone sold their company does not mean they're looking for a next gig, or that they're able to work in the same industry where they might be competing with the sold company.