The Russians, seeking their first medal in the women's Olympic competition, produced four goals in a span of 6:05 of the final period in their opening Group B game.
Sweden, silver medalist eight years ago, survived with a 1-0 victory over Japan in the other Group B contest.
Germany's Franziska Busch delivered the only goal of the opening two periods to give her team a chance for the upset.
Things fell apart in the final period, however, with Russia scoring four times on 10 shots against goalkeeper Viona Harrer.
Iva Gavrilova tied it up 5:04 into the third period and Sosina put Russia in front with the first of her two goals.
In the opening game of the day, the lone goal came from Sweden's Jenni Asserholt with 7:22 left in the first period. Valentina Wallner made that score stand up by stopping 19 shots.
Group A action resumes on Monday with the United States facing Switzerland and Canada taking on Finland. The Americans and Canadians each won their opening game Saturday.