Jamba Juice has finally started up the blenders at its new Rockville store, next to Ruby Tuesday at Federal Plaza on the Pike. In addition to smoothies, the menu includes breakfast foods, sandwiches, wraps and baked pretzels. The Rockville store is a joint venture between the smoothie chain and tennis star Venus Williams, who is working with Jamba Juice as a celebrity spokesperson and D.C.-area franchisee. Williams already has opened two stores in Washington and a third at Westfield Montgomery Mall. She’s expected to make an official appearance at the Rockville store by summer.