HORSE RACING : LET BOB DO IT A GOOD GAMBLE IN THE CINEMA.

Byline: Kevin Modesti Daily News Staff Writer

Ask a silly question - ``What do you like about horse racing?'' - and you get a predictable answer from the man who sets the odds and point spreads for most of the nation's sports bettors.

``Well, the gambling,'' Roxy Roxborough said at Hollywood Park.

Saturday, he particularly enjoyed his wager on Let Bob Do It, a horse he co-owns with Atlantic City Racecourse president Bob Levy, brokerage-firm executive Alex Karkenny and Penn athletic director Steve Bilsky.

Let Bob Do It and jockey Kent Desormeaux cruised to an early lead and won the $136,100 Cinema Handicap, validating the Will Rogers Handicap victory that stamped him as the leading local 3-year-old on turf.

``I didn't bet that much on him,'' Roxborough said in the winner's circle. ``I bet $500 to win.''

Two-dollar players collected $7.20 on Let Bob Do It. Roxborough raked in $1,800.

``I can't bet on sports because it would be a conflict of interest,'' said the boss of Las Vegas Sports Consultants, which sets the lines for three-quarters of the Nevada sportsbooks.

So Roxborough, 45, makes a hobby of visiting racetracks - he's up to 70 in North America - and smoking out winners.

``I've been a horseplayer since I was 19,'' he said. ``I think it's challenging. Some people play golf. I'd rather come out here and spend 4-1/2 hours uncovering mysteries. If I'm wrong in one race, there's another one in a half-hour.''

Roxborough is a small part of the group that bought Let Bob Do It, a Washington-bred gelding, for six figures after a minor stakes victory at Santa Anita. Second in the California Derby, the horse is now 3 for 3 on the L.A. turf courses.

He beat Dr. Sardonica by three-quarters of a length and Winter Quarters by two, running the 1-1/8-mile Cinema in 1:47 2/5.

``I think what makes this one so thrilling,'' said Roxborough, who once co-owned stakes winner Tenacious Tiffany, ``is that the horse has no pedigree, so we didn't expect him to be good.''

Also Saturday, Laffit Pincay rode two winners. The first pulled the 49-year-old jockey within 400 of Bill Shoemaker's record, 8,833 victories. The second came aboard Powis Castle in a three-way photo finish in the $61,250 Rich Cream sprint.

Today, four of the six fillies are listed between 2-1 and 4-1 on the morning line for the $200,000 Gamely Handicap on grass.

Long shot winsEnglish Derby: At Epsom, England, Shaamit, a 12-1 shot, won the 217th English Derby with jockey Michael Hills.