CNN, CBS and NBC declared Romney the victor with 15 percent of the votes counted. The former Massachusetts governor had 62 percent of the vote to 24 percent for Paul, the libertarian Texas congressman, and 7 percent for Gingrich, the conservative former U.S. House speaker from Georgia, CNN reported.
Nineteen delegates were in play in Rhode Island. Romney, generally considered the presumptive nominee, started the day with 695 of the 1,144 he needs to secure the GOP nomination. Gingrich had 141 and Paul 72.
Besides Rhode Island, voters were also casting primary ballots in New York, Pennsylvania, Connecticut and Delaware.
CNN and NBC projected Romney the winner in Connecticut, based on early returns Tuesday.
Romney was expected to cruise to victory since his closest rival, former U.S. Sen. Rick Santorum of Pennsylvania, pulled out of the presidential race April 10.