The ceremony, exactly 60 years after the night the Nazis gassed the final 2,900 Gypsies being held in the camp, also heard warnings that the Sinti and Roma continue to face persistent discrimination, especially in eastern Europe.
"Like the Jews, the Sinti and Roma were brutally persecuted and systematically murdered with an inhuman determination," said Germany's envoy to the ceremony, Environment Minister Juergen Trittin.
"This genocide is part of our history," he said. "As Germans, we carry the historic and the political responsibility."
Up to half a million European Gypsies are believed to have perished at the Nazis' hands during the Second World War, along with six million Jews.
Many were deported to Auschwitz-Birkenau, where the SS set up a special camp section for them.
On August 2, 1944, the SS liquidated the Gypsy camp and killed most of the remaining inmates in the gas chambers. Others were sent to German factories for forced labour.
The anniversary was marked amid the ruins of dozens of prisoner barracks on a vast grassy area, still ringed by concrete fence posts and watchtowers.
"Auschwitz-Birkenau is a symbol of the genocide perpetrated on our people," said Roman Kwiatkowski, the top Gypsy representative in Poland.
Later, several hundred mourners including camp survivors walked from the barracks area to the ruins of a gas chamber, where Gypsy representatives placed candles.
SS soldiers blew up the gas chamber and crematorium in early 1945 when the Nazis abandoned the camp in the face of the Soviet army's westward advance. In May 1945, Nazi Germany surrendered.