Diann Roffe's second run earned her a stunning victory in the women's giant slalom yesterday and gave the U.S. team its first gold medal at the World Alpine Skiing Championships in Santa Caterina Valfurva, Italy.

Roffe, a 17-year-old from Williamson, N.Y., was fifth after the first run in the time of 1 minute 9.18 seconds. She completed her second run -- on a differently laid-out course -- in 1:09.35 for a total time of 2:18.53.

Elisabeth Kirchler of Austria won the silver medal with a combined time of 2:19.13. Eva Twardokens of Squaw Valley, Calif., who led after the first run, won the bronze in 2:19.21 and Debbie Armstrong, the Olympic giant slalom champion from Seattle, finished fourth in 2:19.26.

Roffe is a member of the U.S. B team. Her previous best result was eighth place in a World Cup giant slalom in Lake Placid, N.Y., last year.

The course for the second run, set up by an Austrian coach, had 48 gates and a vertical drop of 343 meters. The first course was set up by American Coach Brad Ghent . . .

Jozef Sabovcik of Czechoslovakia took a big lead in the men's competition after the short program at the European Figure Skating Championships in Goteborg, Sweden. Vladimir Kotin of the Soviet Union was in second place and Fernando Fedronic of France was in third.

In the ice dancing portion of the competition, Natalya Bestemianova and Andrei Bukin of the Soviet Union were the leaders after the compulsory routines. Marina Klimova and Sergei Ponomarenko of the U.S.S.R. were in second place and Britain's Karen Barber and Nicky Slater were in third.