However, Ryan said it's sufficient for the GOP standard-bearer to provide only general principles rather than offer specifics about which tax breaks would be axed so Romney's 20 percent tax cut wouldn't add to the deficit, The Wall Street Journal reported Monday.
"We shouldn't be negotiating the details of tax reform in the middle of a campaign," Ryan said in an interview with the Journal while at Youngstown State University in Ohio.
The Wisconsin congressman and House Budget Committee chairman, said Romney asked him to assume role of working with Congress on fiscal matters if the GOP ticket is elected Nov. 6.
"This is one of the reasons why he asked me to sign on," Ryan said. "It was because of my leadership and the reforms I'd been pushing that he asked me."
The Obama campaign has criticized Romney and Ryan for not telling voters what deductions would be dropped to lower tax rates without adding to the deficit.
In defense, Ryan told the Journal: "What we've learned from experience -- Mitt's experience as governor, my experience doing tax law -- is that you don't go to Congress and say, 'Take it or leave it; here's my plan; pass it.' "You say, 'Here's my framework, here's my objectives. Now, let's figure out together how to accomplish these objectives.' That's how you maximize the possibility of getting things done."
He sidestepped answering whether a proposal that includes raising tax revenue, as long as it was tied to lower marginal rates and cost savings from entitlement programs, would be acceptable.
"It's not as if Republicans haven't offered this before," he said. "But we think the best way to raise revenues is to grow the economy."
Obama campaign spokesman Danny Kanner said Romney and Ryan weren't discussing specifics because "the math doesn't add up without a middle-class tax hike, plain and simple."