Venezuela said unidentified men forcibly abducted Mr Rocha and his whereabouts are unknown.
The human rights group Provea has warned that political repression in Venezuela has intensified since July 29, the day the government-controlled National Electoral Council (CNE) declared President Maduro the winner of the election.
The CNE said Maduro had won a third term with 52 percent of the vote, but did not provide detailed polling station results to back up its claim.
The opposition disputes the CNE's results, saying that according to vote counts collected on election day, opposition candidate Edmundo Gonzalez won 67% of the vote, while Maduro received 30%.
The agency uploaded a copy of its tally online, where it was reviewed by The Washington Post and The Associated Press.
The Washington Post and the Associated Press both reviewed more than 23,000 ballots, or about 80 percent of the total, and concluded that Gonzalez was ahead of Maduro by more than 3.7 million votes.
President Maduro took the matter to the Supreme Court.
A court comprised of Maduro loyalists last week upheld the CNE's decision to allow Maduro to run for a third term.
The court's decision was read by the Chief Justice, an active member of the ruling party.
The UN Human Rights Council has questioned the court's impartiality and independence, accusing it and the CNE of playing a role in the country's repressive system.
Venezuela's opposition coalition called for renewed protests on Wednesday to demand a recount of the vote count.
But there are concerns that the security forces' crackdown on such protests could intensify following the appointment on Tuesday of hardliner Diosdado Cabello as interior, justice and peace minister.
In his new role, Mr Cabello will command Venezuela's feared secret police and national guard.
Mr Cabello has frequently vowed to meet opposition to his government with an iron fist. He has said in the past that Edmundo Gonzalez and Maria Corina Machado should be “behind bars.”
The two opposition leaders have been in hiding for weeks, with Ms Machado only appearing occasionally to address supporters at protest rallies.
On Monday, Ms. Machado urged supporters to keep up the pressure, saying she “will not rest.”
