Barley grains are rich in β-glucan, reducing the risk of metabolic syndromes. Grains of cultivar “Beau Fiber” were step-wisely roasted and pulverized to obtain barley flour with high β-glucan and improved odor. The starch, β-glucan, physicochemical properties, and 26 volatile compounds in each flour sample (Raw and Roasts 1–4) were compared. With the roasting degree, flour particle size decreased, damaged starch increased, and β-glucan molecular weight decreased gradually. Conversely, there were slight decreases in total starch and β-glucan contents. Water absorption of the roasted flours increased and decreased before and after heating at 90 °C, respectively, with the roasting degree. The viscosities of slurries after gelatinization, as well as the temperature and enthalpy of gelatinization, decreased with roasting degree. The odor of barley flours was improved after roasting, and was accompanied by decreasing hexanal and nonanal concentrations, and increasing furfural, pyrazine, and pyrrole concentrations.