"Talk is cheap, I understand how to get America working again," Romney said, The Denver Post reported. "This is not just 'hope.'"
Romney spoke before a crowd of more than 1,000 at the Jefferson County Fairgrounds. He said he had a "presidential accountability scorecard" to help grow the U.S. economy.
The Post said Romney pointed to energy independence, making sure the young have the skills to succeed, improving the U.S. trade system, cutting the national debt and championing small businesses.
If goals in those five areas are achieved, Romney said, it would create an estimated 12 million jobs, the Post reported.
"The economy will come roaring back," Romney said.
Romney said many of the promises U.S. President Barack Obama made four years ago haven't been kept, such as job creation and lowering mortgage rates on homes.
Earlier, aides said Romney was reintroducing his year-old tax plan in Colorado, tailoring it for the middle class.
"He's going to Colorado to talk about his plans for a stronger middle class," said senior adviser Eric Fehrnstrom in a morning conference call, adding Romney would remind voters "the economy is not just downshifting, it's shifting into reverse."
Romney is reintroducing the five elements of his tax plan: energy independence, skills development, trade that works for America, deficit reduction and championing small business. He has proposed reducing tax rates by 20 percent, eliminating the alternative minimum tax, ending the real estate tax and giving lower- and middle-income families a larger tax break for investment income -- all the while keeping it revenue neutral.
A study by the Tax Policy Center estimated unspecified tax exemptions for individuals, deductions and credits would have to be slashed by as much as 66 percent to cover the $360 billion annual cost of the proposed Romney tax code. Campaign economic adviser Kevin Hassett disputed that analysis saying, "Governor Romney has a plan to reduce taxes of all Americans. That's where the job creation will come from."
After his economic speech, Romney joins Republican governors Chris Christie of New Jersey, Bobby Jindal of Louisiana and Wisconsin's Scott Walker at Basalt High School and wraps up the day at an Aspen fundraiser.