In addition to the former presidents, former vice presidents and their spouses were also present.
Roberts said she believes Bush will be remembered for his role in the decline and eventual downfall of the Soviet Union.
Bush appeared to hand former first lady Michelle Obama something at his father's funeral, recreating a moment from Sen.
The current president, who has had a contentious public feud with the Bush family, earlier had declared Wednesday a national day of mourning, closing federal agencies, suspending regular mail delivery and closing stock markets.
'This is the least I could do for President Bush, ' he said.
Mr Clinton talks to Mr Obama
The country said a bid a formal goodbye to Bush on Wednesday in a national funeral service in Washington at the National Cathedral.
After the lack of a simple hello, President Carter nervously checked his watch and turned his head away from the others to chat with his wife, former First Lady Rosalynn Carter.
Another close friend of the elder Bush, former U.S. Senator Alan Simpson, recalled that the 41st president was "a class act from birth to death. one of nature's noble men".
A former Kuwaiti military officer waited five hours in line outside a Houston church just so he could thank and honor George H.W. Bush.
The 43rd United States president had also given Michelle Obama a mint during the memorial service in September for Arizona Senator John McCain.More news: Italy's 'Ndrangheta mafia hit by huge worldwide sweep
More news: Health department reminds residents to get flu shots
More news: Mitchell Marsh dropped by Australia for series opener against India