Jeff Rosen built software for stock trading at private companies, restaurant workflow tools, and injury-prevention tech for athletes and Navy SEALs before co-founding Rhombus, which was later acquired by Chainlink—all after starting out in middle school building calculator games to impress his friends and later teaching AP Calculus in East Oakland through Teach For America, where he also raised money to fly students to visit colleges. At Broom Ventures, he stays deeply hands-on with founders, once staying up until 2 a.m. helping a company prepare fundraising materials, and he graduated from Yale with distinction in Mathematics and Philosophy, winning two research prizes along the way.