Roemer made his announcement at the Hanover Inn on the campus of Dartmouth College, Politico reported. His campaign slogan is "Free to lead" and he has promised to cap campaign contributions at $100.
"I have deliberately chosen a path requiring the help of many because that's the way to win and, more importantly, that's the way to get these mighty things done after the election," Roemer said. "Stand with me against the special interests. Spread the word. It will change."
Roemer served three terms in Congress from 1981 to 1988 as a Democrat. He switched parties three years into his single term as governor from 1988 to 1992.
Roemer's only previous foray into national politics was in 2008 when he took an active part in John McCain's presidential campaign. Early polls show he has little name recognition among Republicans with some surveys putting his support at less than 1 percent.