A roller component and trolley. The trolley component includes the positioning seat, braking part, and roller that are respectively installed on the guiding shaft. The end of the shaft ring is cam surface, putting or relieving pressured to the end of the rollers when bring rotated, forming the braking structure; the trolley includes front bar, rear bar, bottom bar, handle bar, and flexible bag. The roller components are installed on the two sides of the guiding shaft under the rear bar, providing support and facilitating braking of the trolley.