Reading from a list, Romney rattled off the names of his primary challengers and thanked them, saying they "fought hard and well." The list included Newt Gingrich and Ron Paul, who are still campaigning against him.
Sen. John McCain, the party's 2008 nominee, and RNC Chairman Reince Priebus introduced Romney to the gathering of about 200 people. Priebus told Romney that he wanted to welcome him "in a formal way, to greet a family here."
In his speech to the group, Romney criticized David Axelrod, a top Obama adviser, who on Sunday characterized the election as a choice between and economy that "produces a growing middle class and that gives people a chance to get ahead and their kids a chance to get ahead, and an economy that continues down the road we are on."
Reading the remark as casting Obama's economic record in a bad light, Romney said, "I could not agree more."
Romney also met privately with RNC members who had been loyal supporters during the primary process.
Ahead of his speech, three top Romney advisers spent two days meeting with GOP leaders. The party committee has been laying the groundwork for its voter identification programs as well as for a major outreach program to Hispanic voters as the primary process has ground on.
Romney advisers say the integration between the committee and the campaign is going relatively smoothly, as many Romney advisers have close personal ties to RNC staffers or have worked for the committee before.