Jarvis, a 14-year Oracle veteran, was once billed as, having played a vital behind-the-scenes role in shaping the database giant's Internet strategy.
The departure of Roberts, who ceded oversight of North American sales and consulting to Keith Block in September, was widely expected. He had been with the company for 13 years.
Oracle announced the resignations Wednesday in an internal e-mail memo from Ellison, Oracle spokeswoman Jennifer Glass said. Glass added that she didn't know why Jarvis had resigned but that he is expected to take some time off.
Charles Phillips, a former Morgan Stanley software analyst who joined Oracle in May, will now oversee Oracle's marketing efforts, Glass said.
Oracle has seen the departures of several high-level managers in the past few years, fueling speculation that Ellison's management style has spurred some of them to leave. Oracle President Ray Lane left in June 2000 to join powerful Silicon Valley venture capital firm Kleiner Perkins Caufield & Byers, and Executive Vice President Gary Bloom resigned in November 2000 to become chief executive of Veritas Software. Jay Nussbaum, executive vice president of Oracle Service Industries resigned in 2001.