Hi all--got a pretty specific question. I'm hoping to get Ortlieb Front-Roller Classic panniers but want to make sure they'll fit my laptop, a 13" (widescreen) Macbook. The laptop is 12.78", slightly 'taller' than the bag, but I understand the panniers roll closed--would the laptop fit with the bag closed partway? Has anyone tried this and can it be done securely?

Not sure about the macbook's dimensions, but my Panasonic Toughbook T8 fits really well in my front rollers. The dimensions of the T8 are 8.4'' x 10.7''. I can even fit the T8 while in a small laptop case so you might be able to fit a 13".

12"x10" on the back, the roll closure is giving a bit more height to work with.
and the nature of soft sides and bottom will gain some width
over the width of the back.

I have the back-roller classic, and they can easily fit something a little taller than the measured height by just doing a little less rolling. (It may make it a little more likely for water to get in during a downpour the less you roll, though)