Oprah Winfrey's personal chef, Rosie Daley, has been a heavyweight on the bestseller list with In the Kitchen with Rosie, but dinners at Oprah's funky Chicago eatery, the Eccentric, won't see many of Rosie's dishes unless they pick up the book at the gift shop. A host at the restaurant admits there are plenty of requests for the low-calorie cooking, but the Eccentric's chef, Jody Denton, says, ''Rosie's book and Oprah's restaurant have nothing to do with each other. There's probably this perception that (Oprah) comes in and serves the dishes in the book, but that's not true.'' In fact, says the host, ''I haven't even seen her in here recently.'' That's not too surprising: After all, the eatery's signature dish, Oprah's Potatoes (mashed with horseradish, cream, butter, salt and pepper) may be an unfair test of the new-and-improved Oprah's willpower.