To address the labor intensity and potential vegetative damage associated with mechanical picking of Osmanthus fragrans at full bloom, this study proposed a selective separation mechanism using a flexible roller-brush. Biomechanical measurements established a quasi-static operational window, with floral detachment requiring up to 1.2 N and petiole–branch retention remaining above 5.0 N during the observed period. Rigid–flexible coupled transient simulations provided mechanistic support for a flexible unloading effect, predicting approximately 1.3 N at the floral junction and approximately 2.5 N at the petiole–branch junction under the simplified model assumptions. A CZD-01 picker with a three-degree-of-freedom contour-following arm was developed, and a mixed I-Optimal response-surface design was used to identify a candidate-set optimum within the tested three-level factor domain. Bristle configuration was the strongest tested factor affecting immediate leaf detachment (p < 0.0001). Under the selected configuration of 161 r/min roller-brush speed, 8 r/min circumferential speed, and smooth PU bristles, ten validation trials in a flat standardized plantation yielded a flower-picking rate of 84.0 ± 1.38% and an immediate leaf detachment rate of 6.5 ± 0.61%. These results demonstrate promising selective-picking performance under the tested conditions; transferability to other cultivars, seasons, terrains, and long-term tree responses remains to be established.