In 1992, he moved to California to earn a doctorate in engineering at Stanford University (with fellow students in Terry Winograd's group of the same year including Sergey Brin and Larry Page.)
- In 1998, Roscheisen became founder and CEO of eGroups, an email messaging company, which was financed by Sequoia Capital and ultimately acquired by Yahoo for $450 million.
Funded with an initial $10 million, the entity rapidly expanded to a headcount of 50 but shut down by October of the same year to return capital at minimum loss.
Roscheisen raised more than $500 million in capital for Nanosolar (starting with Google founders, LinkedIn founder Reid Hoffman, Zynga founder Mark Pincus, Sunil Paul, VCs USVP and Benchmark Capital, hedge fund manager Steve Cohen at SAC Advisors, Passport Capital, and private equity firm Carlyle Group as well as the world's largest utility EDF and power producer AES), built a 100MW semi fab and a 640MW assembly plant, and secured $4.1 billion in customer supply contracts from EDF (the world's largest utility) and other energy utilities.
[6] Under Roscheisen, Nanosolar became a Silicon Valley flagship company in green technology, widely featured in the media including Fortune,[7] Gigaom,[8] the SJ Merc,[9] Wired,[10] VentureBeat,[11] EDN,[12] Motley Fool's,[13] Business Week,[14] USA Today,[15] and receiving a number of outstanding awards such as the No.