More activity in this frenetic first week of the TV season: CBS premieres two new series, NBC premieres one, and ABC unveils the revamped "Ellen" and the returning "Roseanne."
* "The Cosby Mysteries" (8 p.m.-9 p.m., Channel 2) -- When Bill Cosby made one mystery made-for-TV movie last season, the plan was to spool out a handful each year, much as Peter Falk does with his "Columbo" franchise for ABC. However, the ratings for the first of "The Cosby Mysteries" were high enough to NTC compel NBC to compel Cosby to do it as a weekly series, beginning tonight. Rita Moreno lends support. NBC.
* "Baseball" (8 p.m.-10 p.m., Channel 22) -- This is Inning 4, which covers the 1920s -- and gets deeply into the stories of Babe Ruth, Lou Gehrig and the first broadcasts of baseball. PBS.
* "Beverly Hills, 90210" (8 p.m., Channel 45) -- Dylan (Luke Perry) is turning, this season, into a goat with a goatee -- and tonight he continues his bad behavior by linking up with the show's newest "bad girl": Valerie (Tiffani-Amber Thiessen). Fox.
* "All-American Girl" (8:30 p.m.-9 p.m., Channel 13) -- Last week's premiere episode got the highest ratings of any new show. This second episode, though, is a truer test of things to come. Will those who saw it last week like it enough to return? (Probably.) Will tonight's competing premiere of Dudley Moore's new series on NBC draw away a lot of viewers? (Probably not.) ABC.
* "Daddy's Girls" (8:30 p.m.-9 p.m., Channel 9) -- It's blacked out on Channel 11, though you may be able to catch it on another CBS station. Dudley Moore is, of course, a fine double-take artist, and this new comedy gives him plenty of opportunity to react: He's got three lovely daughters, a bunch of lovely women at work and in his private life, and he's also got Harvey Fierstein, who could well steal the show, Moore or less. CBS.
* "Roseanne" (9 p.m.-9:30 p.m., Channel 13) -- One of the best jokes in this seventh-season premiere comes during the opening credits, when Roseanne -- now going by that single-name identification -- is joined by a long list of one-name co-stars, including "Dan," "Laurie" and "Sara."
* "Touched By an Angel" (9 p.m.-10 p.m., Channel 11) -- This new series doesn't have a prayer. CBS.
* "Ellen" (9:30 p.m.-10 p.m., Channel 13) -- Very funny second-season opener -- and don't switch channels during the closing credits, or you'll miss the best bit of all. ABC.
* "Law & Order" (10 p.m.-11 p.m., Channel 2) -- No more Moriarty: Sam Waterston of "I'll Fly Away" joins the cast as the new assistant district attorney. NBC.
* "Biography: Michelangelo" (8 p.m.-9 p.m., A&E;) -- Coming soon: Biographies of the other Teenage Mutant Ninja Turtles . . .