The Wisconsin congressman laced his comments at an outdoor event in Waukesha Sunday with state references, drawing applause and chuckles from the audience, CNN reported.
Romney, the presumptive GOP nominee, announced his selection of Ryan to be his running mate Saturday.
"My veins run with cheese, bratwurst, and a little Spotted Cow, Leinies [Leinenkugel] and some Millers," he said, referring to Wisconsin brews. "I was raised on the [Green Bay] Packers, [University of Wisconsin] Badgers, [and the Milwaukee] Bucks and Brewers. I like to hunt here, I like to fish here, I like to snowmobile here. I even think ice fishing is -- interesting."
Romney stepped up his attacks against President Obama's re-election effort, telling people in the audience they'd better prepare for the "lowest, meanest, negative campaign in history" by the opposition.
"We're not going to let that happen. This is going to be a campaign about ideas, the future of America. This is a campaign about greatness, about America's future for your children, for the world," Romney said.
"Mr. President, take your campaign out of the gutter and talk about the real issues that America faces," he said.
Romney dressed down a protester who disrupted the event, CNN reported.
"You see. young man, this group here is respectful of other people's right to be heard," Romney said. "And you ought to find yourself a different place to be disruptive because here we believe in listening to people with dignity and respect."