What's up this fall for everybody's favorite legal secretary, Roxanne Melman of L.A. Law? "Oh, she gets hit by a bus," giggles actress Susan Ruttan in a telephone interview.

Not likely, since Ruttan plays the one consistently likable character on the cold-eyed drama about legal eagles.(The season premiere of "L.A. Law" won't be until Thursday, Oct. 18, 9 p.m., Ch. 2.)

Most L.A Law fans relate to Roxanne, who works humbly and ably in an office where greed is the creed. She's a woman gutsy enough to tell off her jerky boss, divorce lawyer Arnie Becker (Corbin Bernsen), who once jockeyed for his dead colleague's office space and has slept with too many clients to count.

Plus, Roxanne is wise enough to know that lawsuits aren't everything in life. She's a source of sanity in a world of intense and bizarre court cases, which last season ranged from white supremacist assaults to people who wanted to be cryogenically frozen.

In the midst of the smart exchanges at the morning conferences, the brilliant closing arguments and the constant office politics, Roxanne displays what Ruttan calls "common sense, everyman" savvy.

"I like that Roxanne has the more realistic point of view of all the characters," she says. "I sometimes think she is the voice of the audience in that she's reacting to those around her who are preoccupied with whether to buy the house in Malibu or make the $20 million financial investment."

Ruttan, who has been with L.A. Law since its 1986 premiere but was referred to as "the secretary" in the first few episodes, has in turn become a popular role model for a number of office workers.

The secretarial skills she displays on the show are for real, by the way. Ruttan married at age 18, and was a widow a short four years later. "I took all the secretary courses in high school," she says. "I was really good at it. In fact, when I moved to Los Angeles I worked as a temporary."

Ruttan says that her own on-the-job experience gave her strong views about what Roxanne was going to be like at work. "I was not about to play her as being sort of a wife, bringing coffee and running errands for Arnie - at least, not without a protest. Roxanne takes pride in her job. She's not brainless and even when she has personal problems, she still does a good job."

As for Roxanne's being smitten with Arnie, Ruttan - sounding like a lawyer - says "their relationship is unresolved. Anyway, it's never been clearly defined."

One of her great fantasies, she says gleefully, is that in the final episode of L.A. Law, Arnie proclaims his love for Rox by saying, "My . . ., I've been a fool!"

Since Arnie's marriage to a woman he represented in a divorce last season, Ruttan says Roxanne's "longing is over for now, since he's still married in these new scripts." But then she coos, with a hint of jealously in her voice, about Arnie's marriage, "It will never last."

Nearly 100 episodes after its premiere, with Emmys in 1987 and 1989 as the outstanding drama series, L.A. Law is about to enter its fifth season with new episodes airing in late October. It is also the top-rated drama among adults for the second consecutive year.

Being a cast member of such a critically acclaimed program has meant movie offers for Ruttan (she co-stars in the about-to-be-released "Funny About Love" with Gene Wilder and Christine Lahti) and four Emmy nominations as outstanding supporting actress in a drama series.

Ruttan has had a strong desire to lose weight though, and, in turn, she's made a clothing change for her L.A. Law counterpart. She lost 45 pounds this past year and had the costumers dress Rox in short skirts in '89.

But romance hasn't been so easy to order for her character. Roxanne shed an insufferably boorish husband, Dave, a few seasons back and is now portrayed mostly as dateless, while the rest of the cast has frisky escapades.

Ruttan says she'll settle for any man, any age for the single Rox. But she adds that this would be most difficult because Roxanne has her elderly father (played by actor Vincent Gardenia) living with her. "Roxanne really doesn't have the freedom to pursue a relationship right now," she says with a sigh.

Ruttan won't reveal upcoming story lines, but she concludes a telephone chat by saying that L.A. Law will add new cast members at the middle of its season.

Another legal secretary in the cast of regulars, perhaps?

"What for?" chides Ruttan. "They got me."