I also am a fan of the rollers - I've got the Front and Rear Roller Pluses. As far as security goes, I just think having the rolled-type dry bag looks harder to get in to, and not as easy for somebody to quickly unclip. Maybe not actually harder, but less familiar. If you're leaving your bike for a few minutes while you run inside a shop, the roll-top just appears less inviting for a quick peep, in my opinion.