Roberts, speaking Saturday in the weekly Republican radio and Internet address, said the appointment of Berwick while the Senate was on vacation over the July Fourth holiday bypasses public hearings Americans deserve on such a key post.
"It is ironic that the president chose Independence Day for this action, avoiding the Senate's constitutional check on executive power, to appoint Dr. Berwick," Roberts said.
"Without a public confirmation hearing on Dr. Berwick's nomination, the Senate and the American people do not have the opportunity to learn about the man who will control one-third of all healthcare spending in America."
Roberts also repeated GOP criticisms of healthcare reform and statements by Berwick, a Harvard University professor, including his remark that healthcare funding plans should redistribute wealth from the richer to the poorest.
"Well, the obvious fear is Dr. Berwick will, in fact, use this position to redistribute the wealth in our country, cementing 'Obamacare' as a giant, but stealthy, income-transfer machine," Roberts said.
Roberts noted Sen. Max Baucus, D-Mont., whose Finance Committee has jurisdiction over the health post and would normally have hearings, had complained he was "troubled" by use of the recess appointment instead of standard Senate confirmation.
"I could not agree more with my Democrat colleague," said Roberts, a member of the Finance Committee as well as the Health, Education, Labor and Pensions Committee.
"We urge the president to reconsider his recess appointment of Dr. Berwick and encourage the Finance Committee to at least hold a public hearing now.
"The president's healthcare plan -- the most sweeping overhaul of healthcare in our lifetime -- cannot be implemented behind closed doors. This is a warning! Your healthcare and the care of your loved ones now hangs in the balance. Americans deserve answers."
Obama defended the appointment of Berwick as head of the Centers for Medicare and Medicaid Services in an NBC interview that aired Friday.
The president said he made his first recess appointment because it was too important to be delayed by "political games."
"There have been more delays, obstruction and stalling when it comes to just appointing people to run the day-to-day aspects of Washington than any president has experienced in history," Obama said. "I can't play political games with the Senate on these issues. I've got a government to run."