Roche heads Irish one-two in Beijing
Ag2r rider Roche pipped RadioShack's Deignan in a final sprint to the line after the three riders had broken away on the final climb of Erpuliang with 15km to go of the stage which began in Men Tou Gou.
Froome was a second back from the Irishmen - who completed the 162km run in three hours, 53 minutes and 15 seconds - and was caught by the chasing group at the death.
It is 27-year-old Roche's first World Tour win and comes towards the end of a season marked by illness and poor form.
Froome is continuing his Vuelta a Espana form - he finished second in the Spanish grand tour - and now stands third, another seven seconds back. His compatriot and Sky team-mate Steve Cummings is fourth (+35s).
The Tour of Beijing is China's first ProTour stage race. The five-stage contest runs until Sunday.