For Sarah Walker, coffee has always been about more than just coffee. She founded Vent Coffee Roasters in 2013, with the goal of letting out the bad and taking in the good. Sarah has been the in-house coffee roaster at Argosy Cafe downtown since 2015, and in the spring she’ll be opening her first brick-and-mortar store in Union Collective, a forthcoming manufacturing and retail complex in Medfield. Sarah talked about the turning point in her relationship with coffee, the sense of community she’s passionate about cultivating, and bringing her knowledge back to Charm City.