Will Rosie O'Donnell (search) be the next Rush Limbaugh (search) or Dr. Laura — by going on radio where the really big bucks are?

The former daytime TV star — who recently launched a gay- family cruise line — is trying out a talk show tomorrow night by subbing for Jim Bohannon Bohannon is syndicated by Viacom/CBS's Westwood One, causing rampant industry speculation that the network is testing O'Donnell for her own radio show.

A Westwood One spokesman couldn't be reached for comment over the weekend.

"I think she'd do fine because she's a colorful, offbeat, opinionated character with a showbiz background, but strong interests in politics and controversial lifestyle issues," said Talkers (search) magazine publisher Michael Harrison.

"However, radio is very demanding," said Harrison, warning that a three-hour talk show, live each day, is not the cakewalk that a batch of pre-taped, hour-long TV shows can be.

If O'Donnell, 42, gets her own radio gig, she'll join a half-dozen TV personalities who've added the medium to their resumes recently — including Marie Osmond, Ryan Seacrest (search), Bill O'Reilly, Al Franken and Janeane Garofalo (search).

It's a new trend, no doubt jump-started by the fact that radio superstars can now command movie-star money, thanks mainly to the economics of a hyper-consolidated industry.

Limbaugh and Howard Stern (search) recently made the Top 30 of Forbes magazine's 100 highest-paid celebrities — with Stern earning an estimated $31 million last year (ranking 28th) and Limbaugh collecting $30 mil (29th).