Besides a possible sixth title for Boca, or a third for Gremio, a berth in the club world championship awaits the winner of Latin America's club championship.
"We are content. We've won the match but now we will rest all week as
there are still 90 minutes left to play," Riquelme said.
He added he was pleased Gremio didn't score in a first leg with the away goal rule.
Seeking the sixth
Teammate Claudio Morel Rodriguez said Boca would not let up in its quest for a sixth Copa title.
"The main thing is to win," he said.
"But Gremio is a hard team and we must keep pressing on."
In the 19th minute, playmaker Riquelme sent a free kick toward striker
Martin Palermo, who ricocheted the ball to Palacio for a left-footed tap into the Gremio net beside the right post.
Video replays showed Palermo arguably offside but the goal was allowed to stand.
Throughout the first half, Gremio and Boca traded scoring threats.
Boca goalkeeper Mauricio Caranta notably used his body to block a scoring attempt by striker Tuta in the 12th.
In the second period, Uruguayan referee Jorge Larrionda expelled Goiano
for a rough kick at Banega, who was not seriously hurt.
Boca then pushed forward to make the most of the numerical advantage.
La Bombonera erupts
In the 73rd, Riquelme sent 45,000 mostly Boca fans wild in the stands at the Argentine club's notoriously intimidating "La Bombonera" stadium as his free kick rocketed past Gremio's Argentine goalkeeper Sebastian Saja, who dove right too late to block the shot.
Undeterred, a Gremio squad that has allowed 10 goals in 12 games, attempted to limit its damage before Ledemsa rounded out the scoring minutes from time.
Riquelme, Boca's star playmaker, was the outstanding figure of the game as he set up Ledesma's final score with a center pass.
Ardent Boca fan and soccer great Diego Maradona was among the crowd raucously cheering from the stands as blue-and-yellow confetti showered down amid a burst of fireworks at the Buenos Aires stadium.
Boca won the Libertadores in 1977, 1978, 2000, 2001 and 2003. Gremio won in 1983 and 1995.