Terms of the deal Monday were not announced.
Earlier in the day the Blazers waived second-year forward Jeff Pendergraph, who injured his knee in the preseason and requires surgery.
The Blazers open the season on Tuesday against the Phoenix Suns at the Rose Garden.
Oberto, a 6-foot-10 native of Argentina, played last season with the Washington Wizards after four seasons with the San Antonio Spurs. He was starting center when the Spurs won the NBA championship in 2007.
Oberto has averaged 3.2 points, 3.5 rebounds, 0.9 assists and 14.6 minutes in 331 NBA games, including 128 starts.
Oberto played on the Argentine national team that won the gold medal at the 2004 Athens Olympics and also the bronze medal-winning team in 2008 Beijing.
Oden and Przybilla were both injured last season and required surgery. Przybilla has already returned to contact practice and is expected to return by mid-November.
Oden played in a five-on-five scrimmage on Monday, but there is no timetable for his return.
The Blazers had planned this season to play Marcus Camby at center, backed up by Pendergraph. But Portland was left thin in the middle when Pendergraph was injured on Oct. 7.
"We want to thank Jeff for his hard work and professionalism since he arrived here in Portland, and we wish him a fast and successful recovery from his injury," said Blazers general manager Rich Cho. "We sometimes have to make difficult decisions in this business, and this was certainly one of them."
Pendergraph averaged 2.7 points and 2.5 rebounds in 39 games, including four starts, as a rookie last season.
The 6-foot-9 forward, who played for Arizona State, was the 31st pick in 2009 and acquired by the Blazers in draft-day trade from Sacramento.
Pendergraph, a fan favorite, took to Twitter after the news, writing, "Thanks blazer fans, I had a great first year with you guys. See yall in the summer maybe."
On Saturday the Blazers traded point guard Jerryd Bayless to New Orleans for a conditional future first-round pick.
Bayless made 11 starts for the Blazers last season, averaging 12.6 points, and has scored 6.8 points per game for his career.
There had been speculation about how the Blazers' roster would look going into the opener. Portland ultimately decided to keep second-year point guard Patty Mills. The team's roster stands at 14 going into the season opener.