Roberts, an accountant from Owensboro, Ky., got into match play Wednesday by surviving a 19-man playoff for the final 16 spots. He then upset top-seeded Mark Harrell of Hazlehurst, Ga.
Playing in his second USGA event, Roberts outlasted Nathan Pistacchio of Fresno, Calif., in 20 holes to advance to the round of 16 Thursday. Then he knocked off William Mitchell of Roswell, Ga., 4 and 3 to reach Friday's round of eight.
Roberts also earned an automatic exemption into the next year's U.S. Amateur Public Links with the win.
Clay Ogden won the 2005 championship as the 63rd seed, the lowest to take the title. Mitchell was the spoiler for local favorite Philip Arouca on Thursday, besting the Wilmette, Ill., resident 4 and 2.
Defending champion Casey Watabu of Kapaa, Hawaii, lost 2 and 1 to Brent Paladino of Kensington, Conn., in the first round, which concluded Thursday morning after play was suspended due to darkness Wednesday.
The quarterfinal and semifinal rounds will be held Friday to determine Saturday's finalists.
The final will be a 36-hole match with the winner likely to receive a 2008 Masters Tournament invitation should he remain an amateur.
Copyright 2007 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.